在我的 Paint App 中，我使用了自定义视图，该视图位于 Finger Paint API 演示中。像这里给出的代码：
public class MyView extends View {
private static final float MINP = 0.25f;
private static final float MAXP = 0.75f;
Paint mPaint;
Bitmap mBitmap;
Canvas mCanvas;
Path mPath;
private Paint mBitmapPaint;
int w, h;
public MyView(Context c) {
super(c);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(0xFFFF0000);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(1);
DisplayMetrics metrics = getContext().getResources()
.getDisplayMetrics();
w = metrics.widthPixels;
h = metrics.heightPixels;
mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
protected void onDraw(Canvas canvas) {
// canvas.drawColor(0xFFAAAAAA);
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
canvas.drawPath(mPath, mPaint);
}
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private void touch_start(float x, float y) {
mPath.reset();
mPath.moveTo(x, y);
mX = x;
mY = y;
}
private void touch_move(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
mX = x;
mY = y;
}
}
private void touch_up() {
mPath.lineTo(mX, mY);
// commit the path to our offscreen
mCanvas.drawPath(mPath, mPaint);
// kill this so we don't double draw
mPath.reset();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}
}
它工作正常，但在我的应用程序中，我放了一个按钮来更改自定义视图的背景，例如......
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (resultCode == RESULT_OK) {
if (requestCode == SELECT_PICTURE) {
Uri selectedImageUri = data.getData();
selectedImagePath = getPath(selectedImageUri);
System.out.println("Image Path===========> : "
+ selectedImagePath);
img = (ImageView) findViewById(R.id.imageBackGround);
// img.setImageURI(selectedImageUri);
try {
Bitmap bmp = BitmapFactory
.decodeStream(getContentResolver().openInputStream(
selectedImageUri));
Bitmap resizedBitmap = Bitmap.createBitmap(bmp, 0, 0,
bmp.getWidth(), bmp.getHeight());
Drawable drawBackground = Drawable.createFromPath(selectedImagePath);
myView.setBackgroundDrawable(drawBackground);
myView.invalidate();
//img.setImageBitmap(resizedBitmap);
//img.setScaleType(ImageView.ScaleType.FIT_XY);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
private String getPath(Uri uri) {
// TODO Auto-generated method stub
String[] projection = { MediaStore.Images.Media.DATA };
Cursor cursor = managedQuery(uri, projection, null, null, null);
if (cursor != null) {
// HERE YOU WILL GET A NULLPOINTER IF CURSOR IS NULL
// THIS CAN BE, IF YOU USED OI FILE MANAGER FOR PICKING THE MEDIA
int column_index = cursor
.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
cursor.moveToFirst();
return cursor.getString(column_index);
} else {
return null;
}
}
使用此代码，我从 SD 卡获取图像并用该图像替换自定义视图背景，在替换背景图像绘制后，手指和绘图路径之间存在一些延迟。