Android开发中遇到ImageButton背景设置的问题

[_zw]

我想在EditUserActivity.java里面，点击一个ImageButton，然后跳到一个fragment，fragment里面有两个按钮，分别是拍照和从相册选择，选择了图片之后，将图片的路径传回给EditUserAcitiviy.java里面，把刚才获得的图片设置为ImageButton的背景图。



错误信息：

09-01 13:55:47.288: I/BBBBBB(14686): 图库
09-01 13:55:55.928: I/TagDialogFragment(14686): imagePath = /storage/sdcard1/baidu/imeface.png
09-01 13:55:55.928: I/@ EditUserActivity.java AAAAAAAAA(14686): /storage/sdcard1/baidu/imeface.png
09-01 13:55:55.928: I/System.out(14686): java.lang.NullPointerException
09-01 13:55:55.928: W/System.err(14686): java.lang.NullPointerException
09-01 13:55:55.928: W/System.err(14686): 	at android.app.Activity.findViewById(Activity.java:1914)
09-01 13:55:55.928: W/System.err(14686): 	at com.example.tracemap.activity.EditUserActivity.toDisplayPhoto(EditUserActivity.java:88)
09-01 13:55:55.928: W/System.err(14686): 	at com.example.tracemap.activity.EditUserActivity.photoUriCallback(EditUserActivity.java:105)
09-01 13:55:55.928: W/System.err(14686): 	at com.example.tracemap.fragment.SelectPhotoDialogFragment.doPhoto(SelectPhotoDialogFragment.java:200)
09-01 13:55:55.928: W/System.err(14686): 	at com.example.tracemap.fragment.SelectPhotoDialogFragment.onActivityResult(SelectPhotoDialogFragment.java:210)
09-01 13:55:55.928: W/System.err(14686): 	at android.support.v4.app.FragmentActivity.onActivityResult(FragmentActivity.java:163)
09-01 13:55:55.928: W/System.err(14686): 	at android.app.Activity.dispatchActivityResult(Activity.java:5530)
09-01 13:55:55.928: W/System.err(14686): 	at android.app.ActivityThread.deliverResults(ActivityThread.java:3589)
09-01 13:55:55.928: W/System.err(14686): 	at android.app.ActivityThread.handleSendResult(ActivityThread.java:3636)
09-01 13:55:55.928: W/System.err(14686): 	at android.app.ActivityThread.access$1600(ActivityThread.java:141)
09-01 13:55:55.928: W/System.err(14686): 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1290)
09-01 13:55:55.928: W/System.err(14686): 	at android.os.Handler.dispatchMessage(Handler.java:102)
09-01 13:55:55.928: W/System.err(14686): 	at android.os.Looper.loop(Looper.java:136)
09-01 13:55:55.928: W/System.err(14686): 	at android.app.ActivityThread.main(ActivityThread.java:5290)
09-01 13:55:55.928: W/System.err(14686): 	at java.lang.reflect.Method.invokeNative(Native Method)
09-01 13:55:55.928: W/System.err(14686): 	at java.lang.reflect.Method.invoke(Method.java:515)
09-01 13:55:55.938: W/System.err(14686): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:859)
09-01 13:55:55.938: W/System.err(14686): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:675)
09-01 13:55:55.938: W/System.err(14686): 	at dalvik.system.NativeStart.main(Native Method)
09-01 13:55:55.938: I/CCCCC(14686): here!

EditUserActivity.java

package com.example.tracemap.activity;

import com.example.tracemap.activity.base.BaseFragmentActivity;
import com.example.tracemap.fragment.SelectPhotoDialogFragment;

public class EditUserActivity extends BaseFragmentActivity {
	private ImageButton btnClose;
	private ImageButton header;
	android.support.v4.app.FragmentManager   mFragmentManager = getSupportFragmentManager();

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_edit_user);


		btnClose = (ImageButton)findViewById(R.id.btn_back);
		header = (ImageButton)findViewById(R.id.header);
		btnClose.setOnClickListener(mOnClickListener);
		header.setOnClickListener(mOnClickListener);
	}

	protected Context getActivity() {
		// TODO Auto-generated method stub
		return this;
	}
	protected void Close()
	{
		this.finish();
	}


	public SelectPhotoDialogFragment.DialogCallback selectPhotoCallback = new  SelectPhotoDialogFragment.DialogCallback (){

		@Override
		public void onSuccess(Bundle data) {
			// TODO Auto-generated method stub
		}

	};
	OnClickListener mOnClickListener = new OnClickListener() {

		@SuppressLint("NewApi")
		@Override
		public void onClick(View v) {
			switch(v.getId())
			{
			case R.id.btn_back:
				Close();
				break;
			case R.id.header:
				SelectPhotoDialogFragment fragment = SelectPhotoDialogFragment.getInstance(selectPhotoCallback);
				Bundle bundle = new Bundle();
				//FragmentTransaction ft = getFragmentManager().beginTransaction();
				//FragmentTransaction ft = getFragmentManager().beginTransaction();
				fragment.show(mFragmentManager, SelectPhotoDialogFragment.TAG);
				break;

			}
		}
	};

	/**
	 * 将选择的图片显示在头像位置
	 * @param photoUri
	 */
	private void toDisplayPhoto(String picPath){

		ImageButton imageButton = (ImageButton)findViewById(R.id.header);
		//Bitmap mHeader = BitmapFactory.decodeStream(getClass().getResourceAsStream(picPath));
		Drawable drawable = Drawable.createFromPath(picPath);
		imageButton.setBackground(drawable);
		//imageButton.setImageResource(R.drawable.ic_camera);
	}


	/**
	 * 回调函数
	 * @param photoUri
	 */
	public void photoUriCallback(String picPath){

		Log.i("@ EditUserActivity.java AAAAAAAAA", picPath);

		//toDisplayPhoto(picPath);
		try {
			toDisplayPhoto(picPath);
		} catch (Exception e) {
			// TODO: handle exception
			Log.i("EditUserActivity.java-line:107", "");
			System.out.println(e);
			e.printStackTrace();
		}
	}



}

SelectPhotoDialogFragment.java

package com.example.tracemap.fragment;

import com.example.tracemap.activity.EditUserActivity;

public class SelectPhotoDialogFragment extends DialogFragment implements OnClickListener {

	public final static String TAG = TagDialogFragment.class.getSimpleName();

	public static final int SELECT_PIC_BY_TACK_PHOTO = 1; // 使用照相机拍照获取图片
	public static final int SELECT_PIC_BY_PICK_PHOTO = 2; // 使用相册中的图片
	public static final String KEY_PHOTO_PATH = "photo_path"; // 从Intent获取图片路径的KEY

	private String picPath; // 获取到的图片路径
	private Uri photoUri;
	private Intent lastIntent;

	DialogCallback mCallback;
	RelativeLayout bg;

	private SelectPhotoDialogFragment(DialogCallback callback) {
		this.mCallback = callback;
	}

	private static SelectPhotoDialogFragment mInstance;

	public synchronized static SelectPhotoDialogFragment getInstance(DialogCallback callback) {
		if (mInstance == null) {
			mInstance = new SelectPhotoDialogFragment(callback);
		}
		return mInstance;
	}

	@SuppressLint("NewApi")
	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

		View view = inflater.inflate(R.layout.fragment_dialog_selectphoto, container, false);

		initView(view);

		return view;
	}


	@Override
	public Dialog onCreateDialog(Bundle savedInstanceState) {
		Dialog dialog = super.onCreateDialog(savedInstanceState);
		dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
		dialog.getWindow().setBackgroundDrawableResource(android.R.color.transparent);
		dialog.setCanceledOnTouchOutside(false);

		dialog.setOnCancelListener(new OnCancelListener() {

			@Override
			public void onCancel(DialogInterface dialog) {
				//
			}
		});
		return dialog;
	}


	private void initView(View view){

		Button btnTakePhoto = (Button) view.findViewById(R.id.btn_take_photo);
		Button btnPickPhoto = (Button) view.findViewById(R.id.btn_pick_photo);

		btnTakePhoto.setOnClickListener(this);
		btnPickPhoto.setOnClickListener(this);
	}

	@Override
	public void onClick(View v) {
		switch (v.getId()) {

		case R.id.btn_take_photo:
			Log.i("AAAAAA", "拍照");
			takePhoto();
			break;
		case R.id.btn_pick_photo:
			Log.i("BBBBBB", "图库");
			pickPhoto();
			break;
			default:break;
		}
	}


	/**
	 * 拍照获取图片
	 */
	private void takePhoto() {

		// 执行拍照之前，先检查SD卡是否存在
		String SDState = Environment.getExternalStorageState();

		if (SDState.equals(Environment.MEDIA_MOUNTED)) {

			Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

			ContentValues values = new ContentValues();
			photoUri = getActivity().getContentResolver().insert(
					MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);
			intent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, photoUri);

			startActivityForResult(intent, SELECT_PIC_BY_TACK_PHOTO);
		} else {
			Toast.makeText(getActivity(), "内存卡不存在", Toast.LENGTH_LONG).show();
		}
	}

	/**
	 * 从相册中取图片
	 */
	private void pickPhoto() {

		Intent intent = new Intent();
		intent.setType("image/*");
		intent.setAction(Intent.ACTION_GET_CONTENT);

		startActivityForResult(intent, SELECT_PIC_BY_PICK_PHOTO);
	}


	public interface DialogCallback {
		public void onSuccess(Bundle data);
	}


	/**
	 * 获取图片的路径
	 */
	private void doPhoto(int requestCode, Intent data) {

		if (requestCode == SELECT_PIC_BY_PICK_PHOTO) {
			if (data == null) {
				Toast.makeText(getActivity(), "选择图片文件出错", Toast.LENGTH_LONG).show();
				return;
			}
			photoUri = data.getData();
			if (photoUri == null) {
				Toast.makeText(getActivity(), "选择图片文件出错", Toast.LENGTH_LONG).show();
				return;
			}
		}


		String[] pojo = { MediaStore.Images.Media.DATA };

		Cursor cursor = getActivity().managedQuery(photoUri, pojo, null, null, null);

		if (cursor != null) {
			int columnIndex = cursor.getColumnIndexOrThrow(pojo[0]);
			cursor.moveToFirst();
			picPath = cursor.getString(columnIndex);

			if(VERSION.SDK_INT < 14) {
			    cursor.close();
			 }
		}

		Log.i(TAG, "imagePath = " + picPath);

		if (picPath != null
				&& (picPath.endsWith(".png") || picPath.endsWith(".PNG")
						|| picPath.endsWith(".jpg") || picPath.endsWith(".JPG"))) {

			//将picPath传给EditUserActivity

			EditUserActivity editUserActivity = new EditUserActivity();
			editUserActivity.photoUriCallback(picPath);
		} else {
			Toast.makeText(getActivity(), "选择图片文件不正确", Toast.LENGTH_LONG).show();
		}
	}

	@Override
	public void onActivityResult(int requestCode, int resultCode, Intent data) {
		// TODO Auto-generated method stub
		if (resultCode == Activity.RESULT_OK) {
			doPhoto(requestCode, data);
			Log.i("CCCCC", "here!");
		}
		super.onActivityResult(requestCode, resultCode, data);
	}

}

[Hare_]

ImageButton imageButton = (ImageButton)findViewById(R.id.header); 确认imageButton 不为空

[baidu_29096973]

跟代码吧！！

[_zw]

引用 1 楼 hjq2013 的回复:

ImageButton imageButton = (ImageButton)findViewById(R.id.header); 确认imageButton 不为空

是的，imageButton不为空。就不知道问题出现在哪里。无论怎么样我都修改不了它的背景。

[_zw]

问题已经找到，在SelectPhotoDialogFragment.java的第170行

EditUserActivity editUserActivity = new EditUserActivity();

这里实例化了多一个EditUserActivity ，导致控件看起来是一样的，但是实际上已经不是同一个Activity的控件了。T_T