答案 -- Android setFocusArea and Auto Focus
我所要做的就是取消之前调用的自动对焦。基本上,正确的操作顺序如下:
protected void focusOnTouch(MotionEvent event) {
if (camera != null) {
camera.cancelAutoFocus();
Rect focusRect = calculateTapArea(event.getX(), event.getY(), 1f);
Rect meteringRect = calculateTapArea(event.getX(), event.getY(), 1.5f);
Parameters parameters = camera.getParameters();
parameters.setFocusMode(Parameters.FOCUS_MODE_AUTO);
parameters.setFocusAreas(Lists.newArrayList(new Camera.Area(focusRect, 1000)));
if (meteringAreaSupported) {
parameters.setMeteringAreas(Lists.newArrayList(new Camera.Area(meteringRect, 1000)));
}
camera.setParameters(parameters);
camera.autoFocus(this);
}}
......更新
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
...
Parameters p = camera.getParameters();
if (p.getMaxNumMeteringAreas() > 0) {
this.meteringAreaSupported = true;
}
...
}
private Rect calculateTapArea(float x, float y, float coefficient) {
int areaSize = Float.valueOf(focusAreaSize * coefficient).intValue();
int left = clamp((int) x - areaSize / 2, 0, getSurfaceView().getWidth() - areaSize);
int top = clamp((int) y - areaSize / 2, 0, getSurfaceView().getHeight() - areaSize);
RectF rectF = new RectF(left, top, left + areaSize, top + areaSize);
matrix.mapRect(rectF);
return new Rect(Math.round(rectF.left), Math.round(rectF.top), Math.round(rectF.right), Math.round(rectF.bottom));
}
private int clamp(int x, int min, int max) {
if (x > max) {
return max;
}
if (x < min) {
return min;
}
return x;
}