數據沒有被填充在textview-Android中

Question

我是Android應用開發者的初學者。首先，我試着用下面的代碼開發一個小應用程序。沒有編譯時或運行時錯誤。但它沒有考慮到我的輸入，也沒有獲得輸出。

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

您已經在計算方法中設置了onclickListener。意味着除非你的計算方法不被調用，否則onClickListener將不會被調用，並且如果onClickListener不會被調用，計算（）方法將不會被調用。

做這個

@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，在所有你應該初始化在的onCreate（）視圖組件，所以在移動這段代碼中創建你已經宣佈這個變量文本視圖之前刪除類型定義。

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); 

不要忘記添加@override您的onClick（）函數，以便您的按鈕水龍頭將運行的onclick功能，所以計算功能。