获取屏幕标题栏和状态栏的高度和实现图片的拖拽效果，图片的缩放效果

Android

- MotionEvent.ACTION_DOWN：在第一个点被按下时触发；

- MotionEvent.ACTION_UP ：当屏幕上唯一的点被放开时触发；

- MotionEvent.ACTION_POINTER_DOWN：当屏幕上已经有一个点被按住，此时再按下其他点时触发。

- MotionEvent.ACTION_POINTER_UP：当屏幕上有多个点被按住，松开其中一个点时触发（即非最后一个点被放开时）。

- MotionEvent.ACTION_MOVE：当有点在屏幕上移动时触发。值得注意的是，由于它的灵敏度很高，而我们的手指又不可能完全静止（即使我们感觉不到移动，但其实我们的手指也在不停地抖 动），所以实际的情况是，基本上只要有点在屏幕上，此事件就会一直不停地被触发。

private View rootView;
private int mActionBarHeight;
private int mNotifiyHeight;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_drag_the_picture);

rootView = getLayoutInflater().inflate(R.layout.activity_drag_the_picture, null);
rootView.post(new Runnable() {
@Override
public void run() {
if (getSupportActionBar() != null){
mActionBarHeight = getSupportActionBar().getHeight();//获取标题栏的高度

//获取状态栏的高度
Rect frame = new Rect();
getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
mNotifiyHeight = frame.top;

System.out.println("notify"+ mNotifiyHeight);

System.out.println(mActionBarHeight);
}else {
mActionBarHeight = 0;
}
}
});

public class DragThePictureActivity extends AppCompatActivity {

private ImageView image;

private View rootView;
private int mActionBarHeight;//标题栏的高度
private int mNotifiyHeight;//状态栏的高度
private int outHeight;//标题栏的高度+状态栏的高度

private float difX;//在图片范围内的点击点的位置的x的坐标和图片左上角的x坐标的距离
private float difY;//在图片范围内的点击点的位置的Y的坐标和图片左上角的Y坐标的距离

private boolean isGO = false;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_drag_the_picture);

rootView = getLayoutInflater().inflate(R.layout.activity_drag_the_picture, null);
rootView.post(new Runnable() {
@Override
public void run() {
if (getSupportActionBar() != null) {
//获取标题栏的高度
mActionBarHeight = getSupportActionBar().getHeight();
} else {
mActionBarHeight = 0;
}

//获取状态栏的高度
Rect frame = new Rect();
getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
mNotifiyHeight = frame.top;

outHeight = mNotifiyHeight + mActionBarHeight;
}
});

image = (ImageView) findViewById(R.id.image);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
int actionMasked = MotionEventCompat.getActionMasked(event);
int pointerIndex = MotionEventCompat.getActionIndex(event);
switch (actionMasked) {
case MotionEvent.ACTION_DOWN:
RelativeLayout.LayoutParams downParams = (RelativeLayout.LayoutParams) image.getLayoutParams();

//判断点击点的位置是否位于图片的实际范围内
if (getTouchX(event, pointerIndex) > downParams.leftMargin
&& getTouchX(event, pointerIndex) < downParams.leftMargin + image.getWidth()
&& getTouchY(event, pointerIndex) > downParams.topMargin + outHeight
&& getTouchY(event, pointerIndex) < downParams.topMargin + image.getHeight() + outHeight) {
System.out.println("In");
isGO = true;

//点击点的X Y 坐标和图片左上角坐标的xy距离
difX = getTouchX(event, pointerIndex) - downParams.leftMargin;
difY = getTouchY(event, pointerIndex) - downParams.topMargin-outHeight;
}

break;

case MotionEvent.ACTION_MOVE:
if (isGO) {
RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) image.getLayoutParams();
params.leftMargin = (int) (getTouchX(event, pointerIndex) - difX);
params.topMargin = (int) (getTouchY(event, pointerIndex) - outHeight-difY);

image.setLayoutParams(params);
}
break;
case MotionEvent.ACTION_UP:
isGO = false;
break;
}
return super.onTouchEvent(event);
}

private float getTouchX(MotionEvent event, int pointerIndex) {
return MotionEventCompat.getX(event, pointerIndex);
}

private float getTouchY(MotionEvent event, int pointerIndex) {
return MotionEventCompat.getY(event, pointerIndex);
}
}

public class MainActivity extends AppCompatActivity {

private ImageView mIv;
private float mTouchAXBefore;
private float mTouchAYBefore;
private float mTouchBXBefore;
private float mTouchBYBefore;
private int mTopMarginBefore;
private int mLeftMarginBefore;
private int mHeightBefore;
private int mWidthBefore;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

mIv = (ImageView) findViewById(R.id.image);
}

@Override
public boolean onTouchEvent(MotionEvent event) {

int actionMasked = MotionEventCompat.getActionMasked(event);

if (MotionEventCompat.getPointerCount(event) == 2) {

switch (actionMasked) {

case MotionEvent.ACTION_POINTER_DOWN:

//缩放前
//获取A点的坐标
mTouchAXBefore = getTouchX(event, 0);
mTouchAYBefore = getTouchY(event, 0);

//获取B点的坐标
mTouchBXBefore = getTouchX(event, 1);
mTouchBYBefore = getTouchY(event, 1);

//获取图片的LayoutPareme
RelativeLayout.LayoutParams paramsBefore = (RelativeLayout.LayoutParams) mIv.getLayoutParams();
mTopMarginBefore = paramsBefore.topMargin;
mLeftMarginBefore = paramsBefore.leftMargin;

//获取图片的宽高
mHeightBefore = mIv.getHeight();
mWidthBefore = mIv.getWidth();

break;

case MotionEvent.ACTION_MOVE:

//缩放后
//获取A点的坐标
float touchAXAfter = getTouchX(event, 0);
float touchAYAfter = getTouchY(event, 0);

//获取B点的坐标
float touchBXAfter = getTouchX(event, 1);
float touchBYAfter = getTouchY(event, 1);

//应用勾股定理
double squareBefore = Math.pow((mTouchAXBefore - mTouchBXBefore), 2)
+ Math.pow((mTouchAYBefore - mTouchBYBefore), 2);
double squareAfter = Math.pow((touchAXAfter - touchBXAfter), 2)
+ Math.pow((touchAYAfter - touchBYAfter), 2);

//缩放比例
double zoomRatio = squareBefore / squareAfter;

//设置图片的LayoutPareme
RelativeLayout.LayoutParams paramsAfter = (RelativeLayout.LayoutParams) mIv.getLayoutParams();

//设置图片的上边距和作边距
paramsAfter.topMargin = (int) (mTopMarginBefore / zoomRatio);
paramsAfter.leftMargin = (int) (mLeftMarginBefore / zoomRatio);

//设置图片的宽高
int heightAfter = (int) (mHeightBefore / zoomRatio);
int widthAfter = (int) (mWidthBefore / zoomRatio);
if (heightAfter > 0 && widthAfter > 0) {
paramsAfter.height = heightAfter;
paramsAfter.width = widthAfter;
mIv.setLayoutParams(paramsAfter);
}
break;
}
}
return super.onTouchEvent(event);
}

private float getTouchX(MotionEvent event, int pointerIndex) {
return MotionEventCompat.getX(event, pointerIndex);
}

private float getTouchY(MotionEvent event, int pointerIndex) {
return MotionEventCompat.getY(event, pointerIndex);
}

}

//布局文件
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.nlte.imagezoom.MainActivity">

<ImageView
android:id="@+id/image"
android:scaleType="centerCrop"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:src="@drawable/image"/>
</FrameLayout>