Question

我正在将自定义视图加载到linearlayout中。自定义视图包含可以定位在线性布局内的图像。在图像定位后，如何确定哪些像素可见？

XML

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/mainView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >


<LinearLayout 
    android:id="@+id/viewPort"
    android:orientation="horizontal"
    android:layout_width="700dp"
    android:layout_height="200dp">
</LinearLayout>

</RelativeLayout>

我的代码加载图片：

    public TouchViewClass(Context context, AttributeSet attrs, int defStyle, String picPath) {
    super(context, attrs, defStyle);
    this.picPath = picPath;

    //decode and size the image.
    mSourceImage = prepareImage();
}
private Bitmap prepareImage(){
    //Create bitmap options
    final BitmapFactory.Options options = new BitmapFactory.Options();


    //Create final bitmap with options specifying the new size
    Bitmap readyImg = BitmapFactory.decodeFile(picPath, options);

    return readyImg;
}
@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    canvas.save();
    canvas.drawBitmap(mSourceImage, mPosX, mPosY, null);
    canvas.restore();
}

和我加载视图的活动

                View touchView = new TouchViewClass(this,mPicturePath);
            LinearLayout rl = (LinearLayout)this.findViewById(R.id.viewPort);
            rl.addView(touchView);

Answer 1

好的想通了。如果其他人试图在被移动之后找到一个绘制的图像，那么我是如何做到的那样

@Override
public boolean onTouchEvent(MotionEvent ev) {
    final int action = ev.getAction();
    switch (action & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN: {
        final float x = ev.getX();
        final float y = ev.getY();

        mLastTouchX = x;
        mLastTouchY = y;


        // Save the ID of this pointer
        mActivePointerId = ev.getPointerId(0);
        break;
    }

    case MotionEvent.ACTION_MOVE: {
        // Find the index of the active pointer and fetch its position
        final int pointerIndex = ev.findPointerIndex(mActivePointerId);
       //Get new location
        final float x = ev.getX(pointerIndex);
        final float y = ev.getY(pointerIndex);

        //Compare to old location
        final float dx = x - mLastTouchX;
        final float dy = y - mLastTouchY;

        //set new resting location
        mPosX += dx;
        mPosY += dy;

        mLastTouchX = x;
        mLastTouchY = y;


        invalidate();
        break;
    }

在自定义视图中查找图像位置

1 个答案: