Android代碼不起作用

Question

我是android新手，下面的代碼被設計爲返回一個名爲「err」的字符串，其中包含輸入中的所有錯誤。遺憾的是，代碼不起作用，並返回一個空字符串。

package com.example.app; 


    //import java.util.Calendar; 

    import android.app.Activity; 
import android.os.Bundle; 

    import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.CheckBox; 
import android.widget.CompoundButton; 
import android.widget.EditText; 
    //import android.widget.DatePicker; 

import android.widget.TextView; 


    public class Second extends Activity implements OnClickListener { 
     CheckBox Facebook_chk; 
     EditText Facebook_name; 
     EditText Name; 
     EditText Id; 
     EditText Txterr; 
     EditText Pass; 
     Button v; 


     /** Called when the activity is first created. */ 
     @Override 
     public void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      this.setContentView(R.layout.second); 
      v = (Button) findViewById(R.id.Btn1); 
      v.setOnClickListener(this); 
      Facebook_chk = (CheckBox)findViewById(R.id.Cfbook);//Represents the facebook checkbox. 
      Facebook_name = (EditText)findViewById(R.id.Face);//represents the facebook text. 
      Name = (EditText)findViewById(R.id.Name);//represents the Name text. 
      Id = (EditText)findViewById(R.id.Id);//represents the Id text. 
      Txterr = (EditText)findViewById(R.id.Txterr);//represents the Id text. 
      Pass = (EditText)findViewById(R.id.Pass);//represents the Pass text. 



     //  final DatePicker Date = (DatePicker)findViewById(R.id.Datepick);//represents the Pass text. 


      Facebook_chk.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener(){ 

       @Override 
       public void onCheckedChanged(CompoundButton buttonView, 
         boolean isChecked) { 
        // TODO Auto-generated method stub 
        if(Facebook_chk.isChecked()) 
         Facebook_name.setEnabled(true); 
        else 
         Facebook_name.setEnabled(false); 
            ; 
          } 
          }); 

      } 


      public String GetErr(){ 

       String error="a"; 
       if(Facebook_name.toString().equals("")&& Facebook_chk.isChecked())//check with title if not available. 
       { 
       error+="facebook account not entered/n";//also check if not available 
       } 
       if((Name.getText().toString().equals(""))) 
       { 
        error+="Name not entered\n"; 


       } 
       if(Id.toString().matches("[a-zA-Z]+") || Id.getText().toString().equals("")) 
        error+="Id entered is invalid\n"; 
       if(Pass.toString().length()<5 || Pass.getText().toString().equals("")) 
        error+="Passwords must contain 5 or more digits\n"; 
      // int day= Date.getDayOfMonth(); 
      // int month = Date.getMonth(); 
      // int year=Date.getYear(); 
       //Calendar enter = Calendar.getInstance(); 
      // Calendar today = Calendar.getInstance(); 
      // enter.set(year,month,day); 
      // today.set(Calendar.YEAR,Calendar.MONTH,Calendar.DAY_OF_MONTH); 
       //if((enter.getTime().before(today.getTime()))) 
       // error+="Date entered either passed or not available."; 

       return error; 
     } 
     @Override 
     public void onClick(View v) { 
      // TODO Auto-generated method stub 
      {//Returns strings,if not empty w print it and stop. 

       if(v.getId()==R.id.Btn1) 
       { 
        if(v.getId() == R.id.Btn1){ 
        String err = GetErr();//THE STRING OF ERROR RETRIEVED. 
        if(err!="a") 
         Txterr.setText(err); 
        else 
         Txterr.setText("all is well"); 
        } 

       } 


      } 
     } 

    } 





      // TODO Auto-generated method stub 

我會比高興更多關於此事的可能的解決方案的進一步指示。

錯誤：

11-09 03:04:21.331: D/dalvikvm(825): GC_FOR_ALLOC freed 39K, 9% free 2885K/3140K, paused 145ms, total 156ms 
11-09 03:04:23.240: D/gralloc_goldfish(825): Emulator without GPU emulation detected. 
11-09 03:11:33.671: D/dalvikvm(825): GC_FOR_ALLOC freed 164K, 11% free 3222K/3596K, paused 75ms, total 94ms 
11-09 03:11:33.873: D/AndroidRuntime(825): Shutting down VM 
11-09 03:11:33.880: W/dalvikvm(825): threadid=1: thread exiting with uncaught exception (group=0x41465700) 
11-09 03:11:33.950: E/AndroidRuntime(825): FATAL EXCEPTION: main 
11-09 03:11:33.950: E/AndroidRuntime(825): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.app/com.example.app.Second}: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.EditText 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211) 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.os.Handler.dispatchMessage(Handler.java:99) 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.os.Looper.loop(Looper.java:137) 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.app.ActivityThread.main(ActivityThread.java:5103) 
11-09 03:11:33.950: E/AndroidRuntime(825): at java.lang.reflect.Method.invokeNative(Native Method) 
11-09 03:11:33.950: E/AndroidRuntime(825): at java.lang.reflect.Method.invoke(Method.java:525) 
11-09 03:11:33.950: E/AndroidRuntime(825): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
11-09 03:11:33.950: E/AndroidRuntime(825): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
11-09 03:11:33.950: E/AndroidRuntime(825): at dalvik.system.NativeStart.main(Native Method) 
11-09 03:11:33.950: E/AndroidRuntime(825): Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.EditText 
11-09 03:11:33.950: E/AndroidRuntime(825): at com.example.app.Second.onCreate(Second.java:41) 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.app.Activity.performCreate(Activity.java:5133) 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
11-09 03:11:33.950: E/AndroidRuntime(825): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175) 
11-09 03:11:33.950: E/AndroidRuntime(825): ... 11 more 
11-09 03:11:37.812: I/Process(825): Sending signal. PID: 825 SIG: 9 
11-09 03:11:51.013: D/dalvikvm(868): GC_FOR_ALLOC freed 42K, 9% free 2885K/3144K, paused 48ms, total 51ms 
11-09 03:11:51.410: D/gralloc_goldfish(868): Emulator without GPU emulation detected. 
11-09 03:11:55.360: D/dalvikvm(868): GC_FOR_ALLOC freed 164K, 11% free 3221K/3596K, paused 60ms, total 65ms 
11-09 03:11:55.600: D/AndroidRuntime(868): Shutting down VM 
11-09 03:11:55.600: W/dalvikvm(868): threadid=1: thread exiting with uncaught exception (group=0x41465700) 
11-09 03:11:55.660: E/AndroidRuntime(868): FATAL EXCEPTION: main 
11-09 03:11:55.660: E/AndroidRuntime(868): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.app/com.example.app.Second}: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.EditText 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211) 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.os.Handler.dispatchMessage(Handler.java:99) 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.os.Looper.loop(Looper.java:137) 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.app.ActivityThread.main(ActivityThread.java:5103) 
11-09 03:11:55.660: E/AndroidRuntime(868): at java.lang.reflect.Method.invokeNative(Native Method) 
11-09 03:11:55.660: E/AndroidRuntime(868): at java.lang.reflect.Method.invoke(Method.java:525) 
11-09 03:11:55.660: E/AndroidRuntime(868): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
11-09 03:11:55.660: E/AndroidRuntime(868): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
11-09 03:11:55.660: E/AndroidRuntime(868): at dalvik.system.NativeStart.main(Native Method) 
11-09 03:11:55.660: E/AndroidRuntime(868): Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.EditText 
11-09 03:11:55.660: E/AndroidRuntime(868): at com.example.app.Second.onCreate(Second.java:41) 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.app.Activity.performCreate(Activity.java:5133) 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
11-09 03:11:55.660: E/AndroidRuntime(868): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175) 
11-09 03:11:55.660: E/AndroidRuntime(868): ... 11 more 
11-09 03:11:58.330: I/Process(868): Sending signal. PID: 868 SIG: 9 
11-09 03:17:20.080: D/dalvikvm(948): GC_FOR_ALLOC freed 46K, 9% free 2885K/3148K, paused 58ms, total 65ms 
11-09 03:17:20.680: D/gralloc_goldfish(948): Emulator without GPU emulation detected. 
11-09 03:24:25.141: D/dalvikvm(948): GC_FOR_ALLOC freed 164K, 11% free 3221K/3596K, paused 85ms, total 99ms 
11-09 03:24:25.340: D/AndroidRuntime(948): Shutting down VM 
11-09 03:24:25.340: W/dalvikvm(948): threadid=1: thread exiting with uncaught exception (group=0x41465700) 
11-09 03:24:25.421: E/AndroidRuntime(948): FATAL EXCEPTION: main 
11-09 03:24:25.421: E/AndroidRuntime(948): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.app/com.example.app.Second}: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.EditText 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211) 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.os.Handler.dispatchMessage(Handler.java:99) 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.os.Looper.loop(Looper.java:137) 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.app.ActivityThread.main(ActivityThread.java:5103) 
11-09 03:24:25.421: E/AndroidRuntime(948): at java.lang.reflect.Method.invokeNative(Native Method) 
11-09 03:24:25.421: E/AndroidRuntime(948): at java.lang.reflect.Method.invoke(Method.java:525) 
11-09 03:24:25.421: E/AndroidRuntime(948): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
11-09 03:24:25.421: E/AndroidRuntime(948): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
11-09 03:24:25.421: E/AndroidRuntime(948): at dalvik.system.NativeStart.main(Native Method) 
11-09 03:24:25.421: E/AndroidRuntime(948): Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.EditText 
11-09 03:24:25.421: E/AndroidRuntime(948): at com.example.app.Second.onCreate(Second.java:41) 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.app.Activity.performCreate(Activity.java:5133) 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
11-09 03:24:25.421: E/AndroidRuntime(948): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175) 
11-09 03:24:25.421: E/AndroidRuntime(948): ... 11 more 
11-09 03:24:28.120: I/Process(948): Sending signal. PID: 948 SIG: 9 

Answer 1

您需要將變量 '錯誤' 初始化字符。嘗試使用佔位符文本「Error =」

如果這就是所有返回的信息，那麼您知道if語句都不是真的。

編輯：

您不正確聲明你的EditText作爲一個TextView。編譯器沒有選擇它，因爲它被轉換爲TextView，這是完全可能的。

您從TextView接收看似隨機的文本的原因是因爲TextView方法'getText()'返回CharSequence。

編輯2：

Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.EditText 11-09 03:11:55.660: E/AndroidRuntime(868): at com.example.app.Second.onCreate(Second.java:41) 

線41 Txterr = (EditText)findViewById(R.id.Txterr);//represents the Id text.

所以，現在你有一個TextView投作爲一個EditText。評估這意味着什麼，並做出正確的改變。