Android program to browse zoom drag and center images automatically
- 2020-10-23 20:17:16
- OfStack
This article describes the Android programming to achieve the image browsing, zooming, dragging and automatic center effect method. To share for your reference, the details are as follows:
Touch.java
/**
* Picture browsing, zooming, dragging, automatic center
*/
public class Touch extends Activity implements OnTouchListener {
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();
DisplayMetrics dm;
ImageView imgView;
Bitmap bitmap;
float minScaleR;// Minimum scale
static final float MAX_SCALE = 4f;// Maximum scaling
static final int NONE = 0;// The initial state
static final int DRAG = 1;// Drag the
static final int ZOOM = 2;// The zoom
int mode = NONE;
PointF prev = new PointF();
PointF mid = new PointF();
float dist = 1f;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.scale);
imgView = (ImageView) findViewById(R.id.imag);// Access controls
bitmap = BitmapFactory.decodeResource(getResources(), this.getIntent()
.getExtras().getInt("IMG"));// Get image resources
imgView.setImageBitmap(bitmap);// Fill in the control
imgView.setOnTouchListener(this);// Set up touch monitor
dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);// Acquired resolution
minZoom();
center();
imgView.setImageMatrix(matrix);
}
/**
* A touch screen monitor
*/
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction() & MotionEvent.ACTION_MASK) {
// Press the main point
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
prev.set(event.getX(), event.getY());
mode = DRAG;
break;
// Click the vice
case MotionEvent.ACTION_POINTER_DOWN:
dist = spacing(event);
// If the distance between two consecutive points is greater than 10 , then it is judged as multi-point mode
if (spacing(event) > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
break;
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
matrix.set(savedMatrix);
matrix.postTranslate(event.getX() - prev.x, event.getY()
- prev.y);
} else if (mode == ZOOM) {
float newDist = spacing(event);
if (newDist > 10f) {
matrix.set(savedMatrix);
float tScale = newDist / dist;
matrix.postScale(tScale, tScale, mid.x, mid.y);
}
}
break;
}
imgView.setImageMatrix(matrix);
CheckView();
return true;
}
/**
* Limit maximum and minimum scaling and center automatically
*/
private void CheckView() {
float p[] = new float[9];
matrix.getValues(p);
if (mode == ZOOM) {
if (p[0] < minScaleR) {
matrix.setScale(minScaleR, minScaleR);
}
if (p[0] > MAX_SCALE) {
matrix.set(savedMatrix);
}
}
center();
}
/**
* Minimum scaling, maximum scaling 100%
*/
private void minZoom() {
minScaleR = Math.min(
(float) dm.widthPixels / (float) bitmap.getWidth(),
(float) dm.heightPixels / (float) bitmap.getHeight());
if (minScaleR < 1.0) {
matrix.postScale(minScaleR, minScaleR);
}
}
private void center() {
center(true, true);
}
/**
* Horizontal and vertical center
*/
protected void center(boolean horizontal, boolean vertical) {
Matrix m = new Matrix();
m.set(matrix);
RectF rect = new RectF(0, 0, bitmap.getWidth(), bitmap.getHeight());
m.mapRect(rect);
float height = rect.height();
float width = rect.width();
float deltaX = 0, deltaY = 0;
if (vertical) {
// If the image is smaller than the screen size, it is displayed in the center. Larger than the screen, the top blank will move up, the bottom blank will move down
int screenHeight = dm.heightPixels;
if (height < screenHeight) {
deltaY = (screenHeight - height) / 2 - rect.top;
} else if (rect.top > 0) {
deltaY = -rect.top;
} else if (rect.bottom < screenHeight) {
deltaY = imgView.getHeight() - rect.bottom;
}
}
if (horizontal) {
int screenWidth = dm.widthPixels;
if (width < screenWidth) {
deltaX = (screenWidth - width) / 2 - rect.left;
} else if (rect.left > 0) {
deltaX = -rect.left;
} else if (rect.right < screenWidth) {
deltaX = screenWidth - rect.right;
}
}
matrix.postTranslate(deltaX, deltaY);
}
/**
* Distance between two points
*/
private float spacing(MotionEvent event) {
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return FloatMath.sqrt(x * x + y * y);
}
/**
* The midpoint of two points
*/
private void midPoint(PointF point, MotionEvent event) {
float x = event.getX(0) + event.getX(1);
float y = event.getY(0) + event.getY(1);
point.set(x / 2, y / 2);
}
}
scale.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_gravity="center" >
<ImageView
android:id="@+id/imag"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_gravity="center"
android:scaleType="matrix" >
</ImageView>
</FrameLayout>
I hope this article has been helpful in Android programming.