1
---------- ------------ UPDATEgetSelectedItem（）。的toString（）返回空值
其中i运行查询是所述部分
public class DatabaseAccess extends MainActivity{
private SQLiteOpenHelper openHelper;
private SQLiteDatabase database;
private static DatabaseAccess instance;
private String courseValue = " course = " + getCourseValue();
private String hungerValue = " hungerLevel = " + getHungerValue();
private String prepValue = " preparationTime " + getPrepValue();
private String cuisineValue = " cuisine = " + getCuisineValue();
/**
* Private constructor to avoid object creation from outside classes.
*
* @param context
*/
private DatabaseAccess(Context context) {
this.openHelper = new DatabaseOpenHelper(context);
}
/**
* Return a singleton instance of DatabaseAccess.
*
* @param context the Context
* @return the instance of DabaseAccess
*/
public static DatabaseAccess getInstance(Context context) {
if (instance == null) {
instance = new DatabaseAccess(context);
}
return instance;
}
/**
* Open the database connection.
*/
public void open() {
this.database = openHelper.getWritableDatabase();
}
/**
* Close the database connection.
*/
public void close() {
if (database != null) {
this.database.close();
}
}
/**
* Read all quotes from the database.
*
* @return a List of quotes
*/
public List<String> getResults() {
List<String> list = new ArrayList<>();
Cursor cursor = database.rawQuery("SELECT foodName FROM foodDB where" + cuisineValue +" &" + hungerValue +" &"+ prepValue +" &"+ courseValue, null);
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
list.add(cursor.getString(0));
cursor.moveToNext();
}
cursor.close();
return list;
}
}
我正在Android Studio创建一个应用程序，我想要获取微调器的值并将其赋值给变量。然而，应用程序总是测试过程中崩溃，并显示：
java.lang.RuntimeException: Unable to start activity ComponentInfo{
com.example.rcadit.foodgenie/com.example.rcadit.foodgenie.resultActivity}:
android.database.sqlite.SQLiteException: near "null":
syntax error (code 1): , while compiling:
SELECT foodName FROM foodDB where cuisine = null
& hungerLevel = null & preparationTime null & course = null
这是我mainActivity.java：
package com.example.rcadit.foodgenie;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.SeekBar;
import android.widget.Spinner;
import android.widget.TextView;
import butterknife.ButterKnife;
import butterknife.InjectView;
public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {
public void onItemSelected(AdapterView<?> parent, View view,
int pos, long id) {
// An item was selected. You can retrieve the selected item using
parent.getItemAtPosition(pos);
}
public void onNothingSelected(AdapterView<?> parent) {
// Another interface callback
}
Toolbar toolbar;
@InjectView(R.id.salty)
SeekBar salty;
private String hungerValue;
private String cuisineValue;
private String prepValue;
private String courseValue;
public void go(View view) {
Intent intent = new Intent(this, resultActivity.class);
startActivity(intent);
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.inject(this);
initToolBar();
saltySlider();
spicySlider();
sweetSlider();
Spinner hunger_spinner = (Spinner) findViewById(R.id.hunger_spinner);
// Create an ArrayAdapter using the string array and a default spinner layout
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
R.array.hunger_level, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
hunger_spinner.setAdapter(adapter);
Spinner cuisine_spinner = (Spinner) findViewById(R.id.cuisine_spinner);
// Create an ArrayAdapter using the string array and a default spinner layout
ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(this,
R.array.cuisine, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
cuisine_spinner.setAdapter(adapter2);
Spinner prep_spinner = (Spinner) findViewById(R.id.time_spinner);
// Create an ArrayAdapter using the string array and a default spinner layout
ArrayAdapter<CharSequence> adapter3 = ArrayAdapter.createFromResource(this,
R.array.preparation_time, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
prep_spinner.setAdapter(adapter3);
Spinner course_spinner = (Spinner) findViewById(R.id.course_spinner);
// Create an ArrayAdapter using the string array and a default spinner layout
ArrayAdapter<CharSequence> adapter4 = ArrayAdapter.createFromResource(this,
R.array.course, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
course_spinner.setAdapter(adapter4);
//give data to variables
hungerValue = hunger_spinner.getSelectedItem().toString();
if (hungerValue.equals("Low")) {
hungerValue = "1";
}
if (hungerValue.equals("Medium")) {
hungerValue = "2";
}
if (hungerValue.equals("High")) {
hungerValue = "3";
}
cuisineValue = cuisine_spinner.getSelectedItem().toString();
prepValue = prep_spinner.getSelectedItem().toString();
if (prepValue.equals("Under 10 mins")) {
prepValue = "< 10";
}
if (prepValue.equals("No Preparation")) {
prepValue = " = 0";
}
if (prepValue.equals("Under 20 mins")) {
prepValue = "< 20";
}
if (prepValue.equals("Under 30 mins")) {
prepValue = "< 30";
}
if (prepValue.equals("Over 30 mins")) {
prepValue = "> 30";
}
courseValue = course_spinner.getSelectedItem().toString();
}
// (...) getters and setter for hungerValue, cuisineValue, prepValue, courseValue
private void saltySlider() {
salty.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
int progressChanged = 0;
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
progressChanged = progress * 50;
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
if (progressChanged < 100/3) {
TextView textView = (TextView) findViewById(R.id.howSalty);
textView.setHint("Not Salty");
}
if (progressChanged > 100/3 & progressChanged < 2 * (100/3)) {
TextView textView = (TextView) findViewById(R.id.howSalty);
textView.setHint("Salty");
}
if (progressChanged > 2 * (100/3)) {
TextView textView = (TextView) findViewById(R.id.howSalty);
textView.setHint("Very Salty");
}
}
});
}
private void sweetSlider() {
SeekBar sweet = (SeekBar) findViewById(R.id.sweet);
sweet.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
int progressChanged = 0;
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
progressChanged = progress * 50;
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
if (progressChanged < 100/3) {
TextView textView = (TextView) findViewById(R.id.howSweet);
textView.setHint("Not Sweet");
}
if (progressChanged > 100/3 & progressChanged < 2 * (100/3)) {
TextView textView = (TextView) findViewById(R.id.howSweet);
textView.setHint("Sweet");
}
if (progressChanged > 2 * (100/3)) {
TextView textView = (TextView) findViewById(R.id.howSweet);
textView.setHint("Very Sweet");
}
}
});
}
private void spicySlider() {
SeekBar spicy = (SeekBar) findViewById(R.id.spicy);
spicy.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
int progressChanged = 0;
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
progressChanged = progress * 50;
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
if (progressChanged < 100/3) {
TextView textView = (TextView) findViewById(R.id.howSpicy);
textView.setHint("Not Spicy");
}
if (progressChanged > 100/3 & progressChanged < 2 * (100/3)) {
TextView textView = (TextView) findViewById(R.id.howSpicy);
textView.setHint("Spicy");
}
if (progressChanged > 2 * (100/3)) {
TextView textView = (TextView) findViewById(R.id.howSpicy);
textView.setHint("Very Spicy");
}
}
});
}
public void initToolBar() {
toolbar = (Toolbar) findViewById(R.id.toolbar);
toolbar.setTitle(R.string.app_name);
setSupportActionBar(toolbar);
}
}
这就是我的全部日志文件：
07/29 15:49:54: Launching app
Cold swapped changes.
$ adb shell am start -n "com.example.rcadit.foodgenie/com.example.rcadit.foodgenie.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Connected to process 3218 on device Nexus_5_API_23_x86 [emulator-5554]
W/System: ClassLoader referenced unknown path: /data/app/com.example.rcadit.foodgenie-1/lib/x86
W/System: ClassLoader referenced unknown path: /data/app/com.example.rcadit.foodgenie-1/lib/x86
D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true
[ 07-29 07:49:57.700 3218: 3218 D/ ]
HostConnection::get() New Host Connection established 0xae8acd80, tid 3218
D/android.widget.GridLayout: horizontal constraints: x2-x0>=792, x2-x1<=308, x1-x0<=325 are inconsistent; permanently removing: x2-x1<=308.
[ 07-29 07:49:57.763 3218: 3236 D/ ]
HostConnection::get() New Host Connection established 0xae8acff0, tid 3236
I/OpenGLRenderer: Initialized EGL, version 1.4
E/Surface: getSlotFromBufferLocked: unknown buffer: 0xaab2cbf0
D/OpenGLRenderer: endAllStagingAnimators on 0xa9f31400 (ListPopupWindow$DropDownListView) with handle 0xad1d5ae0
E/Surface: getSlotFromBufferLocked: unknown buffer: 0xaab2f350
D/OpenGLRenderer: endAllStagingAnimators on 0xa9ef0c00 (ListPopupWindow$DropDownListView) with handle 0xa207d4a0
E/Surface: getSlotFromBufferLocked: unknown buffer: 0xaab2cbf0
D/OpenGLRenderer: endAllStagingAnimators on 0xa9ef5900 (ListPopupWindow$DropDownListView) with handle 0xa207d1a0
E/Surface: getSlotFromBufferLocked: unknown buffer: 0xaab2f350
I/SQLiteAssetHelper: successfully opened database foodfile.sqlite
E/SQLiteLog: (1) near "null": syntax error
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.rcadit.foodgenie, PID: 3218
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.rcadit.foodgenie/com.example.rcadit.foodgenie.resultActivity}: android.database.sqlite.SQLiteException: near "null": syntax error (code 1): , while compiling: SELECT foodName FROM foodDB where cuisine = null & hungerLevel = null & preparationTime null & course = null
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$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$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: android.database.sqlite.SQLiteException: near "null": syntax error (code 1): , while compiling: SELECT foodName FROM foodDB where cuisine = null & hungerLevel = null & preparationTime null & course = null
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:887)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:498)
at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1316)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1255)
at com.example.rcadit.foodgenie.DatabaseAccess.getResults(DatabaseAccess.java:72)
at com.example.rcadit.foodgenie.resultActivity.onCreate(resultActivity.java:21)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$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)
I/Process: Sending signal. PID: 3218 SIG: 9
Application terminated.
我花最后3天试图解决它和在这个论坛上的其他帖子没有为我工作。任何帮助将不胜感激。
您的SQL语句错误。 –
我认为它应该是'prepareTime = null' –
在代码中，您没有包含执行查询的部分 - 并查看错误日志，看起来您的查询语句无效。 '＆'应该是'AND'。 WHERE子句中的'null'值不会导致问题 - 相反，如果没有匹配项，查询应该不返回任何结果。 – ishmaelMakitla