Question

This is my codes below. I’m trying to use intent to call another activity in my pack “Register” in this activity “PictureTakeActivity”. I have another button in this activity, which uses intent to call camera.
The program always stop when I try to call Register.class by clicking the button “GotoRegister”. I’ve added “Register” activity in the manifest.

in DDMS:

Unable to instantiate activity
ComponentInfo{Picture.Capture/Picture.Capture.Register}:
java.lang.NullPointerException

11-21 20:39:08.057: E/AndroidRuntime(539): FATAL EXCEPTION: main
11-21 20:39:08.057: E/AndroidRuntime(539): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{Picture.Capture/Picture.Capture.Register}: java.lang.NullPointerException
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1879)
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.os.Handler.dispatchMessage(Handler.java:99)
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.os.Looper.loop(Looper.java:137)
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.app.ActivityThread.main(ActivityThread.java:4340)
11-21 20:39:08.057: E/AndroidRuntime(539):  at java.lang.reflect.Method.invokeNative(Native Method)
11-21 20:39:08.057: E/AndroidRuntime(539):  at java.lang.reflect.Method.invoke(Method.java:511)
11-21 20:39:08.057: E/AndroidRuntime(539):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
11-21 20:39:08.057: E/AndroidRuntime(539):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
11-21 20:39:08.057: E/AndroidRuntime(539):  at dalvik.system.NativeStart.main(Native Method)
11-21 20:39:08.057: E/AndroidRuntime(539): Caused by: java.lang.NullPointerException
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.app.Activity.findViewById(Activity.java:1794)
11-21 20:39:08.057: E/AndroidRuntime(539):  at Picture.Capture.Register.<init>(Register.java:31)
11-21 20:39:08.057: E/AndroidRuntime(539):  at java.lang.Class.newInstanceImpl(Native Method)
11-21 20:39:08.057: E/AndroidRuntime(539):  at java.lang.Class.newInstance(Class.java:1319)
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
11-21 20:39:08.057: E/AndroidRuntime(539):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1870)
11-21 20:39:08.057: E/AndroidRuntime(539):  ... 11 more

Can anyone help me find the problem?

I’m new to android. How can we debug android program efficiently when using android emulator? Thank you very much.

public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);    
    final Button cameraButton = (Button)findViewById(R.id.camera_button); 
    // Get a handle to the button so we can add a handler for the click event 
    cameraButton.setOnClickListener(new OnClickListener(){
        @Override
        public void onClick(View v){
              String iString = Integer.toString(i+100);
              Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
              File file = new File("/sdcard",iString);
              outputFileUri = Uri.fromFile(file);
              intent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);
              startActivityForResult(intent, TAKE_PICTURE);
              i++;
           }// This will cause the onActivityResult event to fire once it's done

        });

    //Call Register.java

    Button GotoRegister = (Button) findViewById(R.id.GotoRegister);

}

public void registerhandler(View view)
{
    Intent GoRegister = new Intent(PictureTakeActivity.this,Register.class);
          startActivity(GoRegister);
    Toast toast = Toast.makeText(this, "Hello!", Toast.LENGTH_LONG);
    toast.show();
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
 if (requestCode == TAKE_PICTURE) 
  {`

    Uri imageUri = null;

    // Check if the result includes a thumbnail Bitmap
    if (data != null)
    {
      if (data.hasExtra("data")) 
      {
        thumbnail = data.getParcelableExtra("data");
        // TODO Do something with the thumbnail
        SlidingDrawer mysliding= (SlidingDrawer) findViewById(R.id.drawer);
        ImageView myimage= (ImageView) findViewById(R.id.content);
        myimage.setImageBitmap(thumbnail);
        myimage.showContextMenu();
        mysliding.open(); 
      }

    //Problem!!!! This Bitmap does not have any function!
     else {
     // TODO Do something with the full image stored
     // in outputFileUri
        SlidingDrawer mysliding= (SlidingDrawer) findViewById(R.id.drawer);
        ImageView myimage= (ImageView) findViewById(R.id.content);
        myimage.setImageURI(outputFileUri);
        mysliding.open();
        }
     }
  }
}

Register class:

public class Register extends Activity
{
public
TextView RegisterName= (TextView)findViewById(R.id.RegisterName);   
final int PICTURE_ACTIVITY = 1; 



private static int TAKE_PICTURE = 1;
@Override

public void onCreate(Bundle savedInstanceState)
{

    Bitmap bit=Picture.Capture.PictureTakeActivity.thumbnail;

    super.onCreate(savedInstanceState);
    setContentView(R.layout.register_layout);
    RegisterName.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v){

            RegisterName.clearComposingText();
        }


    });

    ImageView Registerimage= (ImageView)findViewById(R.id.RegisterPicture);

    // Relply intent from PictureTakeAcitivity and go Back

    Button GoBack=(Button)findViewById(R.id.GoBack);
    GoBack.setOnClickListener(new View.OnClickListener() {
      public void onClick(View view) {
            Intent replyIntent = new Intent();
            setResult(RESULT_OK, replyIntent);
            finish();
            AddEntry();
        }
    }

    );


}


private void AddEntry()
{
    final Button RegisterButton=(Button)findViewById(R.id.RegisterButton);
    RegisterButton.setOnClickListener
    (new OnClickListener()
     {
        @Override
        public void onClick(View v)
        {
              String EntryName=(String) RegisterName.getText();
              Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
              File file = new File(getFilesDir(),EntryName);
              Uri registryFileUri = Uri.fromFile(file);
              intent.putExtra(MediaStore.EXTRA_OUTPUT, registryFileUri);
              startActivityForResult(intent,TAKE_PICTURE);         
        }           
    }
    );

}

}

Answer 1

TextView RegisterName= (TextView)findViewById(R.id.RegisterName); 

Can’t find the textview before you’ve loaded the layout, put it after :

setContentView(R.layout.register_layout);