如何使用LocalBroadcastManager调用不同的方法

Question

我的操作栏上有3个菜单按钮（add_image，save_meme和share_meme），它们在Mainactivity.java中声明。这些按钮负责在另一个片段中调用相应的方法。使用LocalBroadcastManager建立连接。

public class MainActivity extends AppCompatActivity{
    Intent saveIntent, shareIntent, addImageIntent;
    LocalBroadcastManager localBroadcastManager;

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

        localBroadcastManager = LocalBroadcastManager.getInstance(getApplicationContext());

        addImageIntent = new Intent("ADD_ACTION");
        saveIntent = new Intent("SAVE_ACTION");
        shareIntent = new Intent("SHARE_ACTION");
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()){
            case R.id.add_image:
                localBroadcastManager.sendBroadcast(addImageIntent);
            case R.id.save_meme:
                localBroadcastManager.sendBroadcast(saveIntent);
            case R.id.share_meme:
                localBroadcastManager.sendBroadcast(shareIntent);
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

如上所述，相应的方法在TopImageFragment.java类中。 add_image按钮调用允许用户从设备将图像上传到ImageView的方法：

public void selectedImage() {
    Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.INTERNAL_CONTENT_URI);
    startActivityForResult(intent, PICK_IMAGE);
}

save_meme按钮调用将位图保存到设备的方法：

public void saveMeme(Bitmap btm) {
        counter++;

        File file;
        Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);

        String path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM).getPath();
        file = new File(path + "/Memery/" + timeStamp + counter + ".jpg");
        file.getParentFile().mkdir();

        try {
            OutputStream stream = new FileOutputStream(file);
            btm.compress(Bitmap.CompressFormat.JPEG, 100, stream);
            stream.flush();
            stream.close();
            Toast.makeText(getContext(), "Meme Saved", Toast.LENGTH_SHORT).show();
        } catch (IOException e) {
            e.printStackTrace();
        }

        Uri contentUri = Uri.fromFile(file);
        mediaScanIntent.setData(contentUri);
        Objects.requireNonNull(getContext()).sendBroadcast(mediaScanIntent);
    }

share_meme按钮调用允许用户在各种社交媒体应用程序和电子邮件客户端上共享模因的方法：

public void shareMeme(Bitmap bitmap) {
    String path = MediaStore.Images.Media.insertImage(Objects.requireNonNull(getContext()).getContentResolver(), bitmap, "Meme", null);
    Uri uri = Uri.parse(path);

    Intent share = new Intent(Intent.ACTION_SEND);
    share.setType("image/*");
    share.putExtra(Intent.EXTRA_STREAM, uri);
    share.putExtra(Intent.EXTRA_TEXT, "This is my Meme");
    getContext().startActivity(Intent.createChooser(share, "Share Your Meme!"));
}

但是现在发生的事情是，每当我选择3个菜单按钮中的任何一个时，就会调用所有3个方法。这是我的完整片段：

public class TopImageFragment extends Fragment {

    ImageView imageView;
    TextView topTextView, bottomTextView;
    RelativeLayout topImageRelativeLayout;
    public static final int PICK_IMAGE = 1;
    Uri imageUri;
    int counter = 0;
    String timeStamp = new SimpleDateFormat("yyyyMMdd", Locale.CANADA).format(new Date());
    float textSize, x, imageViewArea, canvasArea;
    double val;


    MemeViewModel memeViewModel;

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_top_image, container, false);

        imageView = view.findViewById(R.id.meme_image_view);

        topTextView = view.findViewById(R.id.top_text_view);
        bottomTextView = view.findViewById(R.id.bottom_text_view);

        topImageRelativeLayout = view.findViewById(R.id.top_image_relative_layout);

        if (savedInstanceState != null) {
            imageUri = savedInstanceState.getParcelable("imageUri");
            imageView.setImageURI(imageUri);
        }
        return view;
    }

    @Override
    public void onSaveInstanceState(@NonNull Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putParcelable("imageUri", imageUri);
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        memeViewModel = ViewModelProviders.of(Objects.requireNonNull(getActivity())).get(MemeViewModel.class);

        memeViewModel.getTopText().observe(getViewLifecycleOwner(), new Observer<CharSequence>() {
            @Override
            public void onChanged(@Nullable CharSequence charSequence) {
                topTextView.setText(charSequence);
            }
        });

        memeViewModel.getBottomText().observe(getViewLifecycleOwner(), new Observer<CharSequence>() {
            @Override
            public void onChanged(@Nullable CharSequence charSequence) {
                bottomTextView.setText(charSequence);
            }
        });
    }

    public void selectedImage() {
        Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.INTERNAL_CONTENT_URI);
        startActivityForResult(intent, PICK_IMAGE);
    }

    public Bitmap getBitmap(ImageView img) {
        BitmapDrawable bitmapDrawable = ((BitmapDrawable) img.getDrawable());
        Bitmap bitmap = bitmapDrawable.getBitmap();

        return bitmap.copy(Bitmap.Config.ARGB_8888, true);
    }

    public Bitmap screenshotMeme() {
        Bitmap image = Bitmap.createBitmap(topImageRelativeLayout.getWidth(), topImageRelativeLayout.getHeight(), Bitmap.Config.RGB_565);
        topImageRelativeLayout.draw(new Canvas(image));

        return image.copy(Bitmap.Config.ARGB_8888, true);
    }

    public Bitmap drawMeme(Bitmap mutableBitmap) {

        String topText = topTextView.getText().toString();
        String bottomText = bottomTextView.getText().toString();

        topText = topText.toUpperCase();
        bottomText = bottomText.toUpperCase();

        Canvas canvas = new Canvas(mutableBitmap);

        TextPaint topFillPaint = new TextPaint();
        TextPaint bottomFillPaint = new TextPaint();

        TextPaint topStrokePaint = new TextPaint();
        TextPaint bottomStrokePaint = new TextPaint();

        Typeface typeface = getResources().getFont(R.font.impact);

        textSize = topTextView.getTextSize();
        imageViewArea = (imageView.getWidth()) * (imageView.getHeight());
        canvasArea = (canvas.getWidth()) * (canvas.getHeight());
        val = textSize * sqrt(canvasArea / imageViewArea);
        x = (float) val;

        topFillPaint.setColor(Color.WHITE);
        topFillPaint.setTextSize(x);
        topFillPaint.setTypeface(typeface);
        topFillPaint.setStyle(Paint.Style.FILL_AND_STROKE);

        topStrokePaint.setStyle(Paint.Style.STROKE);
        topStrokePaint.setStrokeWidth(4);
        topStrokePaint.setTextSize(x);
        topStrokePaint.setColor(Color.BLACK);
        topStrokePaint.setTypeface(typeface);

        bottomFillPaint.setColor(Color.WHITE);
        bottomFillPaint.setTextSize(x);
        bottomFillPaint.setTypeface(typeface);
        bottomFillPaint.setStyle(Paint.Style.FILL_AND_STROKE);

        bottomStrokePaint.setStyle(Paint.Style.STROKE);
        bottomStrokePaint.setStrokeWidth(4);
        bottomStrokePaint.setColor(Color.BLACK);
        bottomStrokePaint.setTextSize(x);
        bottomStrokePaint.setTypeface(typeface);

        StaticLayout topFillLayout = new StaticLayout(topText, topFillPaint, canvas.getWidth(), Layout.Alignment.ALIGN_CENTER,
                0.8f, 0.0f, false);
        StaticLayout topStrokeLayout = new StaticLayout(topText, topStrokePaint, canvas.getWidth(), Layout.Alignment.ALIGN_CENTER,
                0.8f, 0.0f, false);
        StaticLayout bottomFillLayout = new StaticLayout(bottomText, bottomFillPaint, canvas.getWidth(), Layout.Alignment.ALIGN_CENTER,
                0.8f, 0.0f, false);
        StaticLayout bottomStrokeLayout = new StaticLayout(bottomText, bottomStrokePaint, canvas.getWidth(), Layout.Alignment.ALIGN_CENTER,
                0.8f, 0.0f, false);

        topFillLayout.draw(canvas);

        topStrokeLayout.draw(canvas);

        canvas.translate(0, canvas.getHeight() - bottomFillLayout.getHeight());
        bottomFillLayout.draw(canvas);

        bottomStrokeLayout.draw(canvas);

        return mutableBitmap;
    }

    public void saveMeme(Bitmap btm) {
        counter++;

        File file;
        Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);

        String path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM).getPath();
        file = new File(path + "/Memery/" + timeStamp + counter + ".jpg");
        file.getParentFile().mkdir();

        try {
            OutputStream stream = new FileOutputStream(file);
            btm.compress(Bitmap.CompressFormat.JPEG, 100, stream);
            stream.flush();
            stream.close();
            Toast.makeText(getContext(), "Meme Saved", Toast.LENGTH_SHORT).show();
        } catch (IOException e) {
            e.printStackTrace();
        }

        Uri contentUri = Uri.fromFile(file);
        mediaScanIntent.setData(contentUri);
        Objects.requireNonNull(getContext()).sendBroadcast(mediaScanIntent);
    }

    public void shareMeme(Bitmap bitmap) {
        String path = MediaStore.Images.Media.insertImage(Objects.requireNonNull(getContext()).getContentResolver(), bitmap, "Meme", null);
        Uri uri = Uri.parse(path);

        Intent share = new Intent(Intent.ACTION_SEND);
        share.setType("image/*");
        share.putExtra(Intent.EXTRA_STREAM, uri);
        share.putExtra(Intent.EXTRA_TEXT, "This is my Meme");
        getContext().startActivity(Intent.createChooser(share, "Share Your Meme!"));
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (resultCode == RESULT_OK && requestCode == PICK_IMAGE) {
            imageUri = Objects.requireNonNull(data).getData();
            imageView.setImageURI(imageUri);
            memeViewModel.setSharedId(imageUri.getLastPathSegment());
        }
    }

    @Override
    public void onResume() {
        super.onResume();
        LocalBroadcastManager.getInstance(Objects.requireNonNull(getActivity())).registerReceiver(addListener, new IntentFilter("ADD_ACTION"));
        LocalBroadcastManager.getInstance(Objects.requireNonNull(getActivity())).registerReceiver(saveListener, new IntentFilter("SAVE_ACTION"));
        LocalBroadcastManager.getInstance(Objects.requireNonNull(getActivity())).registerReceiver(shareListener, new IntentFilter("SHARE_ACTION"));
    }

    private BroadcastReceiver addListener = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            selectedImage();
        }
    };

    private BroadcastReceiver saveListener = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            float height = getBitmap(imageView).getHeight();
            float width = getBitmap(imageView).getWidth();

            if ((height <= 600) || (width <= 600)) {
                saveMeme(screenshotMeme());
                Toast.makeText(getContext(), "screenshotMeme() method was called", Toast.LENGTH_SHORT).show();
            } else {
                saveMeme(drawMeme(getBitmap(imageView)));
                Toast.makeText(getContext(), "drawMeme() method was called", Toast.LENGTH_SHORT).show();
            }
        }
    };

    private BroadcastReceiver shareListener = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            float height = getBitmap(imageView).getHeight();
            float width = getBitmap(imageView).getWidth();

            if ((height <= 600) || (width <= 600)) {
                shareMeme(screenshotMeme());
                Toast.makeText(getContext(), "screenshotMeme() method was called", Toast.LENGTH_SHORT).show();
            } else {
                shareMeme(drawMeme(getBitmap(imageView)));
                Toast.makeText(getContext(), "drawMeme() method was called", Toast.LENGTH_SHORT).show();
            }
        }
    };

    @Override
    public void onPause() {
        super.onPause();
        LocalBroadcastManager.getInstance(Objects.requireNonNull(getActivity())).unregisterReceiver(addListener);
        LocalBroadcastManager.getInstance(Objects.requireNonNull(getActivity())).unregisterReceiver(saveListener);
        LocalBroadcastManager.getInstance(Objects.requireNonNull(getActivity())).unregisterReceiver(shareListener);
    }
}

Answer 1

问题：因为在切换用例块中，您不返回或放置break语句，所以每当单击菜单项时，它将在切换用例中执行所有语句。

解决方案：：在每种情况下都添加一个return true，以表明您想在单击菜单项时消费该事件。

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()){
        case R.id.add_image:
            localBroadcastManager.sendBroadcast(addImageIntent);
            return true;
        case R.id.save_meme:
            localBroadcastManager.sendBroadcast(saveIntent);
            return true;
        case R.id.share_meme:
            localBroadcastManager.sendBroadcast(shareIntent);
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

或在每种情况下使用break语句，然后在方法末尾返回true。

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()){
        case R.id.add_image:
            localBroadcastManager.sendBroadcast(addImageIntent);
            break;
        case R.id.save_meme:
            localBroadcastManager.sendBroadcast(saveIntent);
            break;
        case R.id.share_meme:
            localBroadcastManager.sendBroadcast(shareIntent);
            break;
        default:
            return super.onOptionsItemSelected(item);
    }

    return true;
}