的Android工作室E/AndroidRuntime：致命异常：主要

-3

此错误来我一直在修改这些点击听众的Android工作室E/AndroidRuntime：致命异常：主要

E/AndroidRuntime: FATAL EXCEPTION: main 
Process: com.example.apple.sqlite, PID: 31591 
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.apple.sqlite/com.example.apple.sqlite.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setKeyListener(android.text.method.KeyListener)' on a null object reference 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setKeyListener(android.text.method.KeyListener)' on a null object reference 
at com.example.apple.sqlite.MainActivity.onCreate(MainActivity.java:46) 
at android.app.Activity.performCreate(Activity.java:6237) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)  
at android.app.ActivityThread.-wrap11(ActivityThread.java)  
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)  
at android.os.Handler.dispatchMessage(Handler.java:102)  
at android.os.Looper.loop(Looper.java:148)  
at android.app.ActivityThread.main(ActivityThread.java:5417)  
at java.lang.reflect.Method.invoke(Native Method)  
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)  
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

MainActivity.java代码

package com.example.apple.sqlite; 

import android.content.Intent; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import java.util.ArrayList; 
import java.util.Calendar; 
import android.app.Activity; 
import android.app.DatePickerDialog; 
import android.app.Dialog; 
import android.os.Bundle; 
import android.view.KeyEvent; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.widget.AdapterView; 
import android.widget.ArrayAdapter; 
import android.widget.Button; 
import android.view.View.OnClickListener; 
import android.widget.DatePicker; 
import android.widget.EditText; 
import android.widget.ListView; 
import android.widget.TextView; 
import android.widget.Toast; 

public class MainActivity extends AppCompatActivity { 

private Calendar calendar; 
private TextView dateView; 
private int year, month, day; 

private ListView obj; 
DBHelper mydb; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 

    mydb = new DBHelper(this); 
    ArrayList array_list = mydb.getAllCotacts(); 
    ArrayAdapter arrayAdapter=new ArrayAdapter(this,android.R.layout.simple_list_item_1, array_list); 

    dateView = (TextView) findViewById(R.id.SQDate); 
    dateView.setKeyListener(null); 
    Button dateButton = (Button)findViewById(R.id.DateButton); 
    calendar = Calendar.getInstance(); 
    year = calendar.get(Calendar.YEAR); 
    month = calendar.get(Calendar.MONTH); 
    day = calendar.get(Calendar.DAY_OF_MONTH); 
    showDate(year, month+1, day); 

    dateButton.setOnClickListener(new View.OnClickListener(){ 
     @Override 
     public void onClick(View view) { 
      final Calendar c = Calendar.getInstance(); 
      year = c.get(Calendar.YEAR); 
      month = c.get(Calendar.MONTH); 
      day = c.get(Calendar.DAY_OF_MONTH); 
      new DatePickerDialog(MainActivity.this, new DatePickerDialog.OnDateSetListener() { 
       @Override 
       public void onDateSet(DatePicker view, int year, int month, int day) { 
        String format = getString(R.string.setdate) + setDateFormat(year,month,day); 
        dateView.setText(format); 
       } 

      }, year,month, day).show(); 
     } 

    }); 

    obj = (ListView)findViewById(R.id.listView1); 
    obj.setAdapter(arrayAdapter); 
    obj.setOnItemClickListener(new AdapterView.OnItemClickListener(){ 
     @Override 
     public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,long arg3) { 
      // TODO Auto-generated method stub 
      int id_To_Search = arg2 + 1; 

      Bundle dataBundle = new Bundle(); 
      dataBundle.putInt("id", id_To_Search); 

      Intent intent = new Intent(getApplicationContext(),DisplayContact.class); 

      intent.putExtras(dataBundle); 
      startActivity(intent); 
     } 
    }); 
} 



private String setDateFormat(int year,int monthOfYear,int dayOfMonth){ 
    return String.valueOf(year) + "-" 
      + String.valueOf(monthOfYear + 1) + "-" 
      + String.valueOf(dayOfMonth); 
} 

public void setDate(View view) { 
    showDialog(999); 
    Toast.makeText(getApplicationContext(), "ca", 
      Toast.LENGTH_SHORT) 
      .show(); 
} 

protected Dialog onCreateDialog(int id) { 
    // TODO Auto-generated method stub 
    if (id == 999) { 
     return new DatePickerDialog(this, 
       myDateListener, year, month, day); 
    } 
    return null; 
} 

private DatePickerDialog.OnDateSetListener myDateListener = new 
     DatePickerDialog.OnDateSetListener() { 
      @Override 
      public void onDateSet(DatePicker arg0, 
            int arg1, int arg2, int arg3) { 
       // TODO Auto-generated method stub 
       // arg1 = year 
       // arg2 = month 
       // arg3 = day 
       showDate(arg1, arg2+1, arg3); 
      } 
     }; 

private void showDate(int year, int month, int day) { 
    dateView.setText(new StringBuilder().append(year).append("-") 
      .append(month).append("-").append(day)); 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.main_menu, menu); 
    return true; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item){ 
    super.onOptionsItemSelected(item); 

    switch(item.getItemId()) { 
     case R.id.item1:Bundle dataBundle = new Bundle(); 
      dataBundle.putInt("id", 0); 

      Intent intent = new Intent(getApplicationContext(),DisplayContact.class); 
      intent.putExtras(dataBundle); 

      startActivity(intent); 
      return true; 
     default: 
      return super.onOptionsItemSelected(item); 
    } 
} 

public boolean onKeyDown(int keycode, KeyEvent event) { 
    if (keycode == KeyEvent.KEYCODE_BACK) { 
     moveTaskToBack(true); 
    } 
    return super.onKeyDown(keycode, event); 
    } 
}

DisplayContact.java代码

package com.example.apple.sqlite; 

import android.app.Activity; 
import android.app.AlertDialog; 
import android.content.DialogInterface; 
import android.content.Intent; 
import android.database.Cursor; 
import android.os.Bundle; 
import android.view.Menu; 
import android.view.MenuInflater; 
import android.view.MenuItem; 
import android.view.View; 
import android.widget.Button; 
import android.widget.TextView; 
import android.widget.Toast; 

/** 
* Created by Apple on 2017/3/5. 
*/ 

public class DisplayContact extends Activity { 
int from_Where_I_Am_Coming = 0; 
private DBHelper mydb ; 

TextView date ; 
TextView item; 
TextView describe; 
TextView money; 
int id_To_Update = 0; 

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_display_contact); 
    date = (TextView) findViewById(R.id.SQDate); 
    item = (TextView) findViewById(R.id.SQItem); 
    describe = (TextView) findViewById(R.id.SQDescribe); 
    money = (TextView) findViewById(R.id.SQMoney); 

    mydb = new DBHelper(this); 

    Bundle extras = getIntent().getExtras(); 
    if(extras !=null) { 
     int Value = extras.getInt("id"); 

     if(Value>0){ 
      //means this is the view part not the add contact part. 
      Cursor rs = mydb.getData(Value); 
      id_To_Update = Value; 
      rs.moveToFirst(); 

      String xdate = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_DATE)); 
      String xitem = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_ITEM)); 
      String xdescribe = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_DESCRIBE)); 
      String xmoney = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_MONEY)); 

      if (!rs.isClosed()) { 
       rs.close(); 
      } 
      Button b = (Button)findViewById(R.id.EnterButton); 
      b.setVisibility(View.INVISIBLE); 

      date.setText((CharSequence)xdate); 
      date.setFocusable(false); 
      date.setClickable(false); 

      item.setText((CharSequence)xitem); 
      item.setFocusable(false); 
      item.setClickable(false); 

      describe.setText((CharSequence)xdescribe); 
      describe.setFocusable(false); 
      describe.setClickable(false); 

      money.setText((CharSequence)xmoney); 
      money.setFocusable(false); 
      money.setClickable(false); 


     } 
    } 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    Bundle extras = getIntent().getExtras(); 

    if(extras !=null) { 
     int Value = extras.getInt("id"); 
     if(Value>0){ 
      getMenuInflater().inflate(R.menu.display_contact, menu); 
     } else{ 
      getMenuInflater().inflate(R.menu.main_menu, menu); 
     } 
    } 
    return true; 
} 

public boolean onOptionsItemSelected(MenuItem items) { 
    super.onOptionsItemSelected(items); 
    switch(items.getItemId()) { 
     case R.id.Edit_Contact: 
      Button b = (Button)findViewById(R.id.EnterButton); 
      b.setVisibility(View.VISIBLE); 
      date.setEnabled(true); 
      date.setFocusableInTouchMode(true); 
      date.setClickable(true); 

      item.setEnabled(true); 
      item.setFocusableInTouchMode(true); 
      item.setClickable(true); 

      describe.setEnabled(true); 
      describe.setFocusableInTouchMode(true); 
      describe.setClickable(true); 

      money.setEnabled(true); 
      money.setFocusableInTouchMode(true); 
      money.setClickable(true); 

      return true; 
     case R.id.Delete_Contact: 

      AlertDialog.Builder builder = new AlertDialog.Builder(this); 
      builder.setMessage(R.string.deleteContact) 
        .setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() { 
         public void onClick(DialogInterface dialog, int id) { 
          mydb.deleteContact(id_To_Update); 
          Toast.makeText(getApplicationContext(), "Deleted Successfully", 
            Toast.LENGTH_SHORT).show(); 
          Intent intent = new Intent(getApplicationContext(),MainActivity.class); 
          startActivity(intent); 
         } 
        }) 
        .setNegativeButton(R.string.no, new DialogInterface.OnClickListener() { 
         public void onClick(DialogInterface dialog, int id) { 
          // User cancelled the dialog 
         } 
        }); 

      AlertDialog d = builder.create(); 
      d.setTitle("Are you sure"); 
      d.show(); 

      return true; 
     default: 
      return super.onOptionsItemSelected(items); 

    } 
} 

/*public void run(View view) { 
    Bundle extras = getIntent().getExtras(); 
    if(extras !=null) { 
     int Value = extras.getInt("id"); 
     if(Value>0){ 
      if(mydb.updateContact(id_To_Update,date.getText().toString(), 
        item.getText().toString(), describe.getText().toString(), 
        money.getText().toString())){ 
       Toast.makeText(getApplicationContext(), "Updated", Toast.LENGTH_SHORT).show(); 
       Intent intent = new Intent(getApplicationContext(),MainActivity.class); 
       startActivity(intent); 
      } else{ 
       Toast.makeText(getApplicationContext(), "not Updated", Toast.LENGTH_SHORT).show(); 
      } 
     } else{ 
      if(mydb.insertContact(date.getText().toString(), item.getText().toString(), 
        describe.getText().toString(), money.getText().toString())){ 
       Toast.makeText(getApplicationContext(), "done", 
         Toast.LENGTH_SHORT).show(); 
      } else{ 
       Toast.makeText(getApplicationContext(), "not done", 
         Toast.LENGTH_SHORT).show(); 
      } 
      Intent intent = new Intent(getApplicationContext(),MainActivity.class); 
      startActivity(intent); 
     } 
    } 
}*/ 
}

后

DBHelper.java代码

package com.example.apple.sqlite; 

import android.content.ContentValues; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.DatabaseUtils; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 

import java.util.ArrayList; 

/** 
* Created by Apple on 2017/3/4. 
*/ 

public class DBHelper extends SQLiteOpenHelper { 

public static final String DATABASE_NAME = "MyDBName.db"; 
public static final String CONTACTS_TABLE_NAME = "contacts"; 
public static final String CONTACTS_COLUMN_ID = "id"; 
public static final String CONTACTS_COLUMN_DATE = "date"; 
public static final String CONTACTS_COLUMN_ITEM = "item"; 
public static final String CONTACTS_COLUMN_DESCRIBE = "describe"; 
public static final String CONTACTS_COLUMN_MONEY = "money"; 

public DBHelper(Context context) { 
    super(context, DATABASE_NAME , null, 1); 
} 

@Override 
public void onCreate(SQLiteDatabase db) { 
    db.execSQL("CREATE TABLE contacts " + 
      "(_id INTEGER PRIMARY KEY NOT NULL , " + 
      "date DATETIME NOT NULL , " + 
      "item VARCHAR, " + 
      "describe VARCHAR," + 
      "money INTEGER)" 
    ); 
} 

public boolean insertContact (String date, String item, String describe, String money) { 
    SQLiteDatabase db = this.getWritableDatabase(); 
    ContentValues contentValues = new ContentValues(); 
    contentValues.put("date", date); 
    contentValues.put("item", item); 
    contentValues.put("describe", describe); 
    contentValues.put("money", money); 
    db.insert("contacts", null, contentValues); 
    return true; 
} 

public Cursor getData(int id) { 
    SQLiteDatabase db = this.getReadableDatabase(); 
    Cursor res = db.rawQuery("select * from contacts where id="+id+"", null); 
    return res; 
} 

public int numberOfRows(){ 
    SQLiteDatabase db = this.getReadableDatabase(); 
    int numRows = (int) DatabaseUtils.queryNumEntries(db, "contacts"); 
    return numRows; 
} 

public boolean updateContact (Integer id, String date, String item, String describe, String money) { 
    SQLiteDatabase db = this.getWritableDatabase(); 
    ContentValues contentValues = new ContentValues(); 
    contentValues.put("date", date); 
    contentValues.put("item", item); 
    contentValues.put("describe", describe); 
    contentValues.put("money", money); 
    db.update("contacts", contentValues, "id = ? ", new String[] { Integer.toString(id) }); 
    return true; 
} 

public Integer deleteContact (Integer id) { 
    SQLiteDatabase db = this.getWritableDatabase(); 
    return db.delete("contacts", 
      "id = ? ", 
      new String[] { Integer.toString(id) }); 
} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    db.execSQL("DROP TABLE IF EXISTS contacts"); 
    onCreate(db); 
} 

public ArrayList<String> getAllCotacts() { 
    ArrayList<String> array_list = new ArrayList<String>(); 

    //hp = new HashMap(); 
    SQLiteDatabase db = this.getReadableDatabase(); 
    Cursor res = db.rawQuery("select * from contacts", null); 
    res.moveToFirst(); 

    while(res.isAfterLast() == false){ 
     array_list.add(res.getString(res.getColumnIndex("contacts"))); 
     res.moveToNext(); 
    } 
    return array_list; 
} 
}

我引用两个Web和创造了这个项目 http://www.tutorialspoint.com/android/android_sqlite_database.htm https://www.tutorialspoint.com/android/android_datepicker_control.htm

我该怎么办？

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    tools:context=".MainActivity"> 

    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/textView" 
     android:layout_alignParentTop="true" 
     android:layout_centerHorizontal="true" 
     android:textSize="30sp" 
     android:text="@string/DataBase" /> 


     <ListView 
      android:id="@+id/listView1" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:layout_centerHorizontal="true" 
      android:layout_centerVertical="true" > 
     </ListView> 

</RelativeLayout>

activity_display_contact.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android= 
    "http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:orientation="vertical" > 
<TextView 
    android:id="@+id/Title" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/enter" 
    android:textSize="26sp" 
    android:textStyle="normal" /> 

    <LinearLayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:orientation="horizontal" > 
    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/item" /> 
    <EditText 
     android:id="@+id/SQItem" 
     android:layout_width="0dip" 
     android:layout_height="wrap_content" 
     android:layout_weight="1" 
     android:hint=""/> 
</LinearLayout> 
<LinearLayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:orientation="horizontal" > 
    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/describe" /> 
    <EditText 
     android:id="@+id/SQDescribe" 
     android:layout_width="0dip" 
     android:layout_height="wrap_content" 
     android:layout_weight="1" 
     android:hint=""/> 
</LinearLayout> 
<LinearLayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:orientation="horizontal" > 
    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/money" /> 
    <EditText 
     android:id="@+id/SQMoney" 
     android:layout_width="0dip" 
     android:layout_height="wrap_content" 
     android:layout_weight="1" 
     android:hint=""/> 
</LinearLayout> 

<LinearLayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:orientation="horizontal" > 
    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/date" /> 
    <EditText 
     android:id="@+id/SQDate" 
     android:layout_width="0dip" 
     android:layout_height="wrap_content" 
     android:layout_weight="1" 
     android:hint=""/> 
</LinearLayout> 

<LinearLayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:orientation="horizontal"> 

    <Button 
     android:id="@+id/EnterButton" 
     style="@style/AppTheme" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/news" /> 

    <Button 
     android:id="@+id/DateButton" 
     style="@style/AppTheme" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/choose" /> 

    <Button 
     android:id="@+id/CancelButton" 
     style="@style/AppTheme" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/cancel" /> 
</LinearLayout> 

</LinearLayout>

来源

2017-03-05 林園龍

检查你r用于数据的基础上 –

处理空值意味着你[R存储什么都或获取vcalue为空 –

检查您是否确实在activity_main.xml中有ID为SQDate的TextView – tahsinRupam

在你的布局activity_main.xml，有没有与任何android:id="@+id/SQDate" TextView的？

我猜你是想调用的TextView从另一个.XML

编辑：

你的观点是，ID = SQDate不是一个TextView，它是一个EditText。

在您的MainActivity类别，改变这种：

private TextView dateView;

和

dateView = (TextView) findViewById(R.id.SQDate);

要：

private EditText dateView;

和

dateView = (EditText) findViewById(R.id.SQDate);

来源

2017-03-05 07:07:39

我发布我的activity_main。xml –

@林园龙只需按照我编辑的答案中的步骤... –

我尝试TextView更改EditText –

改变你的TextView标识在activity_main.xml中

到SQDate替换：

android:id="@+id/textView"

有了：

android:id="@+id/SQDate"

来源

2017-03-05 07:35:50 tahsinRupam

谢谢我知道该怎么办 –

@林园龙如果这个答案对你有帮助，你可以把它标记为已接受。它将在未来帮助其他人。 – tahsinRupam

其实......这不是答案。解决方案只是SQdate不nuder activity_main.xml –

的Android工作室E/AndroidRuntime：致命异常：主要

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