我正在尝试实现一个图像视图，该图像视图显示我在SignatureActivity类中绘制的签名。我在网上收到错误：
bitmap.compress(CompressFormat.PNG, 90, mFileOutStream);
public class SignatureActivity extends AppCompatActivity {
Button mClear, mGetSign, mCancel;
File file;
LinearLayout mContent;
View view;
signature mSignature;
Bitmap bitmap;
// Creating Separate Directory for saving Generated Images
String DIRECTORY = Environment.getExternalStorageDirectory().getPath() + "/UserSignature/";
String pic_name = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.getDefault()).format(new Date());
String StoredPath = DIRECTORY + pic_name + ".png";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_signature);
mContent = (LinearLayout) findViewById(R.id.canvasLayout);
mSignature = new signature(getApplicationContext(), null);
mSignature.setBackgroundColor(Color.WHITE);
// Dynamically generating Layout through java code
mContent.addView(mSignature, ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
mClear = (Button) findViewById(R.id.clear);
mGetSign = (Button) findViewById(R.id.getsign);
mGetSign.setEnabled(false);
mCancel = (Button) findViewById(R.id.cancel);
view = mContent;
mGetSign.setOnClickListener(onButtonClick);
mClear.setOnClickListener(onButtonClick);
mCancel.setOnClickListener(onButtonClick);
// Method to create Directory, if the Directory doesn't exists
file = new File(DIRECTORY);
if (!file.exists()) {
file.mkdir();
}
}
Button.OnClickListener onButtonClick = new Button.OnClickListener() {
@Override
public void onClick(View v) {
if (v == mClear) {
Log.v("log_tag", "Panel Cleared");
mSignature.clear();
mGetSign.setEnabled(false);
} else if (v == mGetSign) {
Log.v("log_tag", "Panel Saved");
if (Build.VERSION.SDK_INT >= 23) {
isStoragePermissionGranted();
} else {
view.setDrawingCacheEnabled(true);
mSignature.save(view, StoredPath);
Toast.makeText(getApplicationContext(), "Successfully Saved", Toast.LENGTH_SHORT).show();
// Calling the same class
recreate();
}
} else if(v == mCancel){
Log.v("log_tag", "Panel Canceled");
// Calling the BillDetailsActivity
Intent intent = new Intent(SignatureActivity.this, MainActivity.class);
startActivity(intent);
}
}
};
public boolean isStoragePermissionGranted() {
if (Build.VERSION.SDK_INT >= 23) {
if (getApplicationContext().checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
return true;
} else {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
return false;
}
} else {
return true;
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
view.setDrawingCacheEnabled(true);
mSignature.save(view, StoredPath);
Toast.makeText(getApplicationContext(), "Successfully Saved", Toast.LENGTH_SHORT).show();
// Calling the same class
recreate();
}
else
{
Toast.makeText(this, "The app was not allowed to write to your storage. Hence, it cannot function properly. Please consider granting it this permission", Toast.LENGTH_LONG).show();
}
}
public class signature extends View {
private static final float STROKE_WIDTH = 5f;
private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;
private Paint paint = new Paint();
private Path path = new Path();
private float lastTouchX;
private float lastTouchY;
private final RectF dirtyRect = new RectF();
public signature(Context context, AttributeSet attrs) {
super(context, attrs);
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(STROKE_WIDTH);
}
public void save(View v, String StoredPath) {
Log.v("log_tag", "Width: " + v.getWidth());
Log.v("log_tag", "Height: " + v.getHeight());
if (bitmap == null) {
bitmap = Bitmap.createBitmap(mContent.getWidth(), mContent.getHeight(), Bitmap.Config.RGB_565);
}
Canvas canvas = new Canvas(bitmap);
try {
// Output the file
FileOutputStream mFileOutStream = new FileOutputStream(StoredPath);
v.draw(canvas);
// Convert the output file to Image such as .png
bitmap.compress(CompressFormat.PNG, 90, mFileOutStream);
Intent intent = new Intent(SignatureActivity.this, MainActivity.class);
intent.putExtra("imagePath", StoredPath);
startActivity(intent);
finish();
mFileOutStream.flush();
mFileOutStream.close();
} catch (Exception e) {
Log.v("log_tag", e.toString());
}
}
public void clear() {
path.reset();
invalidate();
mGetSign.setEnabled(false);
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(path, paint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = event.getX();
float eventY = event.getY();
mGetSign.setEnabled(true);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
path.moveTo(eventX, eventY);
lastTouchX = eventX;
lastTouchY = eventY;
return true;
case MotionEvent.ACTION_MOVE:
case MotionEvent.ACTION_UP:
resetDirtyRect(eventX, eventY);
int historySize = event.getHistorySize();
for (int i = 0; i < historySize; i++) {
float historicalX = event.getHistoricalX(i);
float historicalY = event.getHistoricalY(i);
expandDirtyRect(historicalX, historicalY);
path.lineTo(historicalX, historicalY);
}
path.lineTo(eventX, eventY);
break;
default:
debug("Ignored touch event: " + event.toString());
return false;
}
invalidate((int) (dirtyRect.left - HALF_STROKE_WIDTH),
(int) (dirtyRect.top - HALF_STROKE_WIDTH),
(int) (dirtyRect.right + HALF_STROKE_WIDTH),
(int) (dirtyRect.bottom + HALF_STROKE_WIDTH));
lastTouchX = eventX;
lastTouchY = eventY;
return true;
}
private void debug(String string) {
Log.v("log_tag", string);
}
private void expandDirtyRect(float historicalX, float historicalY) {
if (historicalX < dirtyRect.left) {
dirtyRect.left = historicalX;
} else if (historicalX > dirtyRect.right) {
dirtyRect.right = historicalX;
}
if (historicalY < dirtyRect.top) {
dirtyRect.top = historicalY;
} else if (historicalY > dirtyRect.bottom) {
dirtyRect.bottom = historicalY;
}
}
private void resetDirtyRect(float eventX, float eventY) {
dirtyRect.left = Math.min(lastTouchX, eventX);
dirtyRect.right = Math.max(lastTouchX, eventX);
dirtyRect.top = Math.min(lastTouchY, eventY);
dirtyRect.bottom = Math.max(lastTouchY, eventY);
}
}
}
任何帮助将不胜感激。我创建了一个线程，但是它仍然无法正常工作。
new Thread() {
@Override
public void run() {
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
bitmap.compress(CompressFormat.PNG, 90, mFileOutStream);
}}.start();
通过更改用于授予设备许可权的代码解决了该错误
Button.OnClickListener onButtonClick = new Button.OnClickListener() {
@Override
public void onClick(View v) {
if (v == mClear) {
Log.v("log_tag", "Panel Cleared");
mSignature.clear();
mGetSign.setEnabled(false);
} else if (v == mGetSign) {
Log.v("log_tag", "Panel Saved");
if (Build.VERSION.SDK_INT >= 23 && checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
isStoragePermissionGranted();
} else {
view.setDrawingCacheEnabled(true);
mSignature.save(view, StoredPath);
Toast.makeText(getApplicationContext(), "Successfully Saved", Toast.LENGTH_SHORT).show();
// Calling the same class
recreate();
}
} else if(v == mCancel){
Log.v("log_tag", "Panel Canceled");
// Calling the BillDetailsActivity
Intent intent = new Intent(SignatureActivity.this, MainActivity.class);
startActivity(intent);
}
}
};
您正在主（UI）线程上调用bitmap.compress方法，这可能会阻塞主线程并导致UI冻结。要解决此问题，您应该在后台（工作）线程上运行此代码-无论如何，您都应该这样做，因为您还在执行文件I / O，这也可能阻塞主线程。
[使用AsyncTask，执行程序，线程，处理程序等有多种方法来执行此操作。您可以在官方文档here中找到一些信息。