数据没有被填充在textview-Android中

Question

我是Android应用开发者的初学者。首先，我试着用下面的代码开发一个小应用程序。没有编译时或运行时错误。但它没有考虑到我的输入，也没有获得输出。

package com.example.myfirstapp; 

import android.os.Bundle; 
//import android.view.View.OnClickListener; 
import android.app.Activity; 
import android.view.Menu; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.RadioButton; 
import android.widget.TextView; 
/*import android.widget.Toast; 
import android.app.Activity; 
import android.view.Menu;*/ 

public class MainActivity extends Activity implements OnClickListener{ 
    //private EditText text; 
    RadioButton mileButton,kmhButton ; 
    TextView textview1,textview2; 
    Button calcButton; 
    private View.OnClickListener droidTapListener; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

     System.out.println("HIIIIIIIIII"); 

     setContentView(R.layout.activity_main); 
     //text = (EditText) findViewById(R.id.textView1); 
     } 



    @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); 
     //getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    public void calculate() { 

    mileButton = (RadioButton) findViewById(R.id.radio0); //radiobutton objects 
     kmhButton = (RadioButton) findViewById(R.id.radio1); 

     calcButton = (Button) findViewById(R.id.button1);  //button obj 
     calcButton.setOnClickListener(droidTapListener); //setting up click listeners. 

     TextView textview1 = (TextView) findViewById(R.id.textView1); 
     TextView textview2 = (TextView) findViewById(R.id.textView2); 
     /*if(text.getText().length()==0) 
      System.out.println("Empty Value");*/ 

     if(textview1.getText().length()==0) 
      System.out.println("Enter a valid input."); 

     /*Toast.makeText(this, "enter a valid number", Toast.LENGTH_LONG) 
     .show(); */ 

     double inputValue = Double.parseDouble(textview1.getText().toString()); 
     if (mileButton.isChecked()) { 
      //text.setText(String.valueOf(convertToMiles(inputValue))); 
      double res= convertToMiles(inputValue); 
      String finalresult = new Double(res).toString(); 
      textview2.setText(finalresult); 

      System.out.println("RESULT"+finalresult); 

      // uncheck "to miles" Button 
      mileButton.setChecked(false); 
      // check "to km/h" Button 
      kmhButton.setChecked(true); 
     } else { /* if kmhButton isChecked() */ 
      //text.setText(String.valueOf(convertToKmh(inputValue))); 
      double res= convertToKmh(inputValue); 
      String finalresult = new Double(res).toString(); 
      textview2.setText(finalresult); 

      System.out.println("RESULT"+finalresult); 

      // uncheck "to km/h" Button 
      kmhButton.setChecked(false); 
      // check "to miles" Button 
      mileButton.setChecked(true); 

     } 
    } 



private double convertToMiles(double inputValue) { 
    // convert km/h to miles 
    double res=inputValue * 1.609344; 
    return res; 

    //return (inputValue * 1.609344); 
} 

private double convertToKmh(double inputValue) { 
    // convert miles to km/h 
    return (inputValue * 0.621372); 
    } 

public void onClick(View v) { 
    calculate(); 
} 
} 

Answer 1

您已经在计算方法中设置了onclickListener。意味着除非你的计算方法不被调用，否则onClickListener将不会被调用，并且如果onClickListener不会被调用，计算（）方法将不会被调用。

做这个

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    System.out.println("HIIIIIIIIII"); 

    setContentView(R.layout.activity_main); 
    //text = (EditText) findViewById(R.id.textView1); 

    calcButton = (Button) findViewById(R.id.button1);  
    calcButton.setOnClickListener(droidTapListener); 

    } 

Answer 2

首先，在所有你应该初始化在的onCreate（）视图组件，所以在移动这段代码中创建你已经宣布这个变量文本视图之前删除类型定义。

mileButton = (RadioButton) findViewById(R.id.radio0); //radiobutton objects 
    kmhButton = (RadioButton) findViewById(R.id.radio1); 

    calcButton = (Button) findViewById(R.id.button1);  //button obj 
    calcButton.setOnClickListener(this); //you droidTapListener isn't initialize and you implements clickListener so use this for listening this event. 
    textview1 = (TextView) findViewById(R.id.textView1); 
    textview2 = (TextView) findViewById(R.id.textView2); 

不要忘记添加@override您的onClick（）函数，以便您的按钮水龙头将运行的onclick功能，所以计算功能。