Android - 在屏幕上移动 ImageView（如拖动）

Question

我正在尝试创建一个应用程序，它可以像拖动一样在您的设备上移动 ImageView，例如，当我将 75% 的 ImageView 移出屏幕时，会显示 Toast。我一直在阅读有关MotionEvent 和onTouchListener 的信息，并且我已经关注了question，但这并不能说服我。

编辑

我当前的代码是：

public class MainActivity extends AppCompatActivity implements View.OnTouchListener {

    int windowwidth;
    int windowheight;
    private ImageView mImageView;
    private ViewGroup mRrootLayout;
    private int _xDelta;
    private int _yDelta;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        DisplayMetrics displaymetrics = new DisplayMetrics();
        this.getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
        windowwidth = displaymetrics.widthPixels;
        windowheight = displaymetrics.heightPixels;
        mRrootLayout = (ViewGroup) findViewById(R.id.root);
        mImageView = (ImageView) mRrootLayout.findViewById(R.id.im_move_zoom_rotate);

        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(150, 150);
        mImageView.setLayoutParams(layoutParams);
        mImageView.setOnTouchListener(this);
    }
    public boolean onTouch(View view, MotionEvent event) {
        final int X = (int) event.getRawX();
        final int Y = (int) event.getRawY();
        if(X == 0){
            Toast.makeText(this, "OUT", Toast.LENGTH_SHORT).show();
        }
        else if (Y == 0){
            Toast.makeText(this, "OUT", Toast.LENGTH_SHORT).show();
        }
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
                _xDelta = X - lParams.leftMargin;
                _yDelta = Y - lParams.topMargin;
                break;
            case MotionEvent.ACTION_UP:
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                break;
            case MotionEvent.ACTION_POINTER_UP:
                break;
            case MotionEvent.ACTION_MOVE:
                RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view
                        .getLayoutParams();
                layoutParams.leftMargin = X - _xDelta;
                layoutParams.topMargin = Y - _yDelta;
                layoutParams.rightMargin = -250;
                layoutParams.bottomMargin = -250;
                view.setLayoutParams(layoutParams);
                break;
        }
        mRrootLayout.invalidate();
        return true;
    }
}

我做了那些if 和else if 只是为了知道ImageView 是否正在离开设备，在设备的左侧和右侧似乎没问题，但我想成功更干净而不是硬写，我也没有得到LayoutParams(150,150)为什么是150？我也不明白为什么我必须创建一个RelativeLayout.LayoutParams 以及为什么我必须放

layoutParams.rightMargin = -250;
layoutParams.bottomMargin = -250;

我做了if/else if，因为我想在用户想要将ImageView从设备中取出时删除，所以我需要控制他何时尝试，目前我只得到它TOP/LEFT/对不对，我还获取设备的尺寸只是为了尝试 X 或 Y 是否与高度或宽度相同，只是显示 Toast 但它没有正确执行。

现在我的ImageView 是ic_launcher，但它会更大（几乎是中间屏幕）。

注意

如果您知道任何其他更简单或更简洁的方法，请随时将其放在这里，我不在乎我的代码，我可以调整它，我只是希望它清晰而不是硬编码。

Answer 1

您的日常工作大部分时间都有效。在下面的代码中，我已经注释掉了不需要的部分，并对需要解释的部分进行了注释。这是成品的样子：

此图说明了如何计算左边距。相同类型的计算适用于上边距。

MainActivity.java

public class MainActivity extends AppCompatActivity implements View.OnTouchListener {

    int windowwidth; // Actually the width of the RelativeLayout.
    int windowheight; // Actually the height of the RelativeLayout.
    private ImageView mImageView;
    private ViewGroup mRrootLayout;
    private int _xDelta;
    private int _yDelta;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // We are interested when the image view leaves its parent RelativeLayout
        // container and not the screen, so the following code is not needed.
//        DisplayMetrics displaymetrics = new DisplayMetrics();
//        this.getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
//        windowwidth = displaymetrics.widthPixels;
//        windowheight = displaymetrics.heightPixels;
        mRrootLayout = (ViewGroup) findViewById(R.id.root);
        mImageView = (ImageView) mRrootLayout.findViewById(R.id.im_move_zoom_rotate);

        // These these following 2 lines that address layoutparams set the width
        // and height of the ImageView to 150 pixels and, as a side effect, clear any
        // params that will interfere with movement of the ImageView.
        // We will rely on the XML to define the size and avoid anything that will
        // interfere, so we will comment these lines out. (You can test out how a layout parameter
        // can interfere by setting android:layout_centerInParent="true" in the ImageView.
//        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(150, 150);
//        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(150, 150);
//        mImageView.setLayoutParams(layoutParams);
        mImageView.setOnTouchListener(this);

        // Capture the width of the RelativeLayout once it is laid out.
        mRrootLayout.post(new Runnable() {
            @Override
            public void run() {
                windowwidth = mRrootLayout.getWidth();
                windowheight = mRrootLayout.getHeight();
            }
        });
    }

    // Tracks when we have reported that the image view is out of bounds so we
    // don't over report.
    private boolean isOutReported = false;

    public boolean onTouch(View view, MotionEvent event) {
        final int X = (int) event.getRawX();
        final int Y = (int) event.getRawY();

        // Check if the image view is out of the parent view and report it if it is.
        // Only report once the image goes out and don't stack toasts.
        if (isOut(view)) {
            if (!isOutReported) {
                isOutReported = true;
                Toast.makeText(this, "OUT", Toast.LENGTH_SHORT).show();
            }
        } else {
            isOutReported = false;
        }
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                // _xDelta and _yDelta record how far inside the view we have touched. These
                // values are used to compute new margins when the view is moved.
                _xDelta = X - view.getLeft();
                _yDelta = Y - view.getTop();
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_POINTER_DOWN:
            case MotionEvent.ACTION_POINTER_UP:
                // Do nothing
                break;
            case MotionEvent.ACTION_MOVE:
                RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams) view
                    .getLayoutParams();
                // Image is centered to start, but we need to unhitch it to move it around.
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
                    lp.removeRule(RelativeLayout.CENTER_HORIZONTAL);
                    lp.removeRule(RelativeLayout.CENTER_VERTICAL);
                } else {
                    lp.addRule(RelativeLayout.CENTER_HORIZONTAL, 0);
                    lp.addRule(RelativeLayout.CENTER_VERTICAL, 0);
                }
                lp.leftMargin = X - _xDelta;
                lp.topMargin = Y - _yDelta;
                // Negative margins here ensure that we can move off the screen to the right
                // and on the bottom. Comment these lines out and you will see that
                // the image will be hemmed in on the right and bottom and will actually shrink.
                lp.rightMargin = view.getWidth() - lp.leftMargin - windowwidth;
                lp.bottomMargin = view.getHeight() - lp.topMargin - windowheight;
                view.setLayoutParams(lp);
                break;
        }
        // invalidate is redundant if layout params are set or not needed if they are not set.
//        mRrootLayout.invalidate();
        return true;
    }

    private boolean isOut(View view) {
        // Check to see if the view is out of bounds by calculating how many pixels
        // of the view must be out of bounds to and checking that at least that many
        // pixels are out.
        float percentageOut = 0.50f;
        int viewPctWidth = (int) (view.getWidth() * percentageOut);
        int viewPctHeight = (int) (view.getHeight() * percentageOut);

        return ((-view.getLeft() >= viewPctWidth) ||
            (view.getRight() - windowwidth) > viewPctWidth ||
            (-view.getTop() >= viewPctHeight) ||
            (view.getBottom() - windowheight) > viewPctHeight);
    }
}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/root"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/im_move_zoom_rotate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:src="@drawable/circle" />

</RelativeLayout>

Answer 2

该框架有一个名为View.OnDragListener 的类。请参阅Drag & Drop 教程。

如果您想研究如何做到这一点，另请参阅DraggablePanel 项目。

Answer 3

如何使用 onTouch 移动 RelativeLayout 中包含的所有视图的工作示例。希望它会有所帮助：

public class MainActivity extends AppCompatActivity implements View.OnTouchListener {
    private RelativeLayout mRelLay;
    private float mInitialX, mInitialY;
    private int mInitialLeft, mInitialTop;
    private View mMovingView = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mRelLay = (RelativeLayout) findViewById(R.id.relativeLayout);

        for (int i = 0; i < mRelLay.getChildCount(); i++)
            mRelLay.getChildAt(i).setOnTouchListener(this);
    }

    @Override
    public boolean onTouch(View view, MotionEvent motionEvent) {
        RelativeLayout.LayoutParams mLayoutParams;

        switch (motionEvent.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mMovingView = view;
                mLayoutParams = (RelativeLayout.LayoutParams) mMovingView.getLayoutParams();
                mInitialX = motionEvent.getRawX();
                mInitialY = motionEvent.getRawY();
                mInitialLeft = mLayoutParams.leftMargin;
                mInitialTop = mLayoutParams.topMargin;
                break;

            case MotionEvent.ACTION_MOVE:
                if (mMovingView != null) {
                    mLayoutParams = (RelativeLayout.LayoutParams) mMovingView.getLayoutParams();
                    mLayoutParams.leftMargin = (int) (mInitialLeft + motionEvent.getRawX() - mInitialX);
                    mLayoutParams.topMargin = (int) (mInitialTop + motionEvent.getRawY() - mInitialY);
                    mMovingView.setLayoutParams(mLayoutParams);
                }
                break;

            case MotionEvent.ACTION_UP:
                mMovingView = null;
                break;
        }

        return true;
    }
}

Answer 4

我正在使用这个方法来拖动一个 ImageView ，希望对你有帮助： 所以我定义了类的那些属性：

 private float xCoOrdinate, yCoOrdinate;
 private double screenCenterX, screenCenterY;

然后我在activity的OnCreate()方法下实现这段代码：

 mRrootLayout.getBackground().setAlpha(255);

    /**
     * Calculate max hypo value and center of screen.
     */
    final DisplayMetrics display = getResources().getDisplayMetrics();
    screenCenterX = display.widthPixels / 2;
    screenCenterY = (display.heightPixels - getStatusBarHeight()) / 2;
    final double maxHypo = Math.hypot(screenCenterX, screenCenterY);

    mImageView.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            /**
             * Calculate hypo value of current imageview position according to center
             */
            double centerYPos = mImageView.getY() + (mImageView.getHeight() / 2);
            double centerXPos = mImageView.getX() + (mImageView.getWidth() / 2);
            double a = screenCenterX - centerXPos;
            double b = screenCenterY - centerYPos;
            double hypo = Math.hypot(a, b);

            /**
             * change alpha of background of layout
             */
            alpha = (int) (hypo * 255) / (int) maxHypo;
            if (alpha < 255)
                mRrootLayout.getBackground().setAlpha(255 - alpha);

            switch (event.getActionMasked()) {
                case MotionEvent.ACTION_DOWN:
                    xCoOrdinate = mImageView.getX() - event.getRawX();
                    yCoOrdinate = mImageView.getY() - event.getRawY();
                    break;
                case MotionEvent.ACTION_MOVE:
                    mImageView.animate().x(event.getRawX() + xCoOrdinate).y(event.getRawY() + yCoOrdinate).setDuration(0).start();
                    break;
                case MotionEvent.ACTION_UP:
                     if (alpha > 50) {
                        Toast.makeText(ImageViewerActivity.this, "Out", Toast.LENGTH_SHORT).show();
                        return false;
                    } else {
                        Toast.makeText(ImageViewerActivity.this, "In", Toast.LENGTH_SHORT).show();
                        mImageView.animate().x(0).y((float) screenCenterY - mImageView.getHeight() / 2).setDuration(100).start();
                        mRrootLayout.getBackground().setAlpha(255);
                    }
                default:
                    return false;
            }
            return true;
        }
    });

Answer 5

更新

在步骤 3 中添加右/下边距以防止图像缩放。 您可以看到如果您不更改右/下边距，图像将按相对布局缩放。

1. getMeasuredHeight/Width 避免MATCH_PARENT 和WRAP_CONTENT。
2. 如果有工具栏/操作栏，则topMargin + height > relativeLayout's height 也适用于底部确定。

3. out of bound的记录状态避免toast连续出现。

   public class MainActivity extends AppCompatActivity implements View.OnTouchListener {
   
       Point lastPoint = new Point();
       RelativeLayout relativeLayout;
   
       boolean lastOutOfTop = false;
       boolean lastOutOfLeft = false;
       boolean lastOutOfRight = false;
       boolean lastOutOfBottom = false;
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
           (findViewById(R.id.imageView)).setOnTouchListener(this);
           relativeLayout = (RelativeLayout)findViewById(R.id.relativeLayout);
       }
   
       @Override
       public boolean onTouch(View view, MotionEvent event) {
           //1. user's finger
           final Point point = new Point((int) event.getRawX(), (int) event.getRawY());
   
           switch (event.getAction() & MotionEvent.ACTION_MASK) {
               case MotionEvent.ACTION_DOWN:
                   // 2. record the last touch point
                   lastPoint = point;
                   break;
               case MotionEvent.ACTION_UP:
                   break;
               case MotionEvent.ACTION_POINTER_DOWN:
                   break;
               case MotionEvent.ACTION_POINTER_UP:
                   break;
               case MotionEvent.ACTION_MOVE:
                   // 3. get the move offset
                   final Point offset = new Point(point.x-lastPoint.x, point.y-lastPoint.y);
                   RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view
                           .getLayoutParams();
                   layoutParams.leftMargin += offset.x;
                   layoutParams.topMargin += offset.y;
                   // * also check right/bottom Margin
                   layoutParams.rightMargin = relativeLayout.getMeasuredWidth() - layoutParams.leftMargin+view.getMeasuredWidth();
                   layoutParams.bottomMargin = relativeLayout.getMeasuredHeight() - layoutParams.topMargin+view.getMeasuredHeight();
                   view.setLayoutParams(layoutParams);
                   // 4. record the last touch point
                   lastPoint = point;
                   break;
           }
   
           // 5. check bounds
           RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
           boolean outOfTop = layoutParams.topMargin < 0;
           boolean outOfLeft = layoutParams.leftMargin < 0;
           boolean outOfBottom = layoutParams.topMargin+view.getMeasuredHeight() > relativeLayout.getMeasuredHeight();
           boolean outOfRight = layoutParams.leftMargin+view.getMeasuredWidth() > relativeLayout.getMeasuredWidth();
   
           // 6. if out of bound
           if (outOfLeft&&!lastOutOfLeft) Toast.makeText(this, "OUT Left", Toast.LENGTH_SHORT).show();
           if (outOfTop&&!lastOutOfTop) Toast.makeText(this, "OUT Top", Toast.LENGTH_SHORT).show();
           if (outOfBottom&&lastOutOfBottom) Toast.makeText(this, "OUT Bottom", Toast.LENGTH_SHORT).show();
           if (outOfRight&&lastOutOfRight)  Toast.makeText(this, "OUT Right", Toast.LENGTH_SHORT).show();
   
           // 7. record
           lastOutOfTop = outOfTop;
           lastOutOfLeft = outOfLeft;
           lastOutOfBottom = outOfBottom;
           lastOutOfRight = outOfRight;
           return true;
       }
   }
   

Answer 6

您可以通过此代码实现此目的。

DisplayMetrics metrics = getResources().getDisplayMetrics();
int windowWidth = metrics.widthPixels;
int windowHeight = metrics.heightPixels;

现在在您的 onTouch 方法中，计算目标位置是否超过上述尺寸。

if(currentXLocation + deltaX > windowWidth){

// this will ensure that target location 
// is always <= windowHeight
deltaX = windowWidth - currentXLocation; 

} else if( currentXLocation + deltaX < 0){

deltaX = -(currentXLocation);

} else if (...){

// perform similar calculations for the rest 

}