Android Bitmap rotates around a point

You need to use the positioning function in the project, that is, to rotate a point around the center of a circle. The function that views the canvas has only one canvas. drawBitmap (bitmap, matrix, paint) is rotated by using Matrix. Here, a demo is implemented. The function is to draw an original source clockwise and undo this circle counterclockwise, which is implemented by Timer. The Code is as follows: Surface. java is a class for drawing graphics.

Package com. example. test; import java. util. timer; import java. util. timerTask; import android. annotation. suppressLint; import android. content. context; import android. graphics. bitmap; import android. graphics. bitmapFactory; import android. graphics. canvas; import android. graphics. color; import android. graphics. matrix; import android. graphics. paint; import android. graphics. pixelFormat; import android. gr Aphics. porterDuff. mode; import android. OS. handler; import android. OS. message; import android. util. log; import android. view. surfaceHolder; import android. view. surfaceView; import android. view. surfaceHolder. callback; @ SuppressLint ("HandlerLeak") class Surface extends SurfaceView implements Callback {Bitmap bmp; private Paint mPaint; private SurfaceHolder mHolder; public Surface (Context context) {su Per (context); mHolder = getHolder (); mHolder. addCallback (this); mPaint = new Paint (); mPaint. setColor (Color. GREEN); mPaint. setAntiAlias (true); // setFocusable (true); setFocusableInTouchMode (true); // setZOrderOnTop (true); // mHolder. setFormat (PixelFormat. TRANSPARENT); // set the background to TRANSPARENT bmp = BitmapFactory. decodeResource (getResources (), R. drawable. camera_r_local); bmp = Bitmap. createScaledBitmap (bmp, 15, 1 5, false);} public Handler handler = new Handler () {@ Override public void handleMessage (Message msg) {switch (msg. what) {case 0: canvas_ OK (); break;} super. handleMessage (msg) ;}}; public void canvas_ OK () {Canvas canvas = null; try {canvas = mHolder. lockCanvas (); canvas. drawColor (Color. TRANSPARENT, Mode. CLEAR); // CLEAR the screen // canvas. save (); Matrix matrix = new Matrix (); matrix. postTranslate (130, 0); Matrix. postRotate (degree, 130,130); canvas. drawBitmap (bmp, matrix, mPaint); // canvas. restore ();} catch (Exception e) {} finally {if (canvas! = Null) {mHolder. unlockCanvasAndPost (canvas) ;}} int degree = 0; Timer timer = new Timer (); boolean flag = true; @ Override public void surfaceCreated (SurfaceHolder holder) {canvas_ OK (); timer. schedule (new TimerTask () {@ Override public void run () {if (flag) {degree ++; if (degree = 360) {flag = false ;}} else {degree --; if (degree =-360 | degree = 0) {flag = true ;}} Log. e ("flag", degr Ee + ":" + flag); handler. sendEmptyMessage (0) ;}}, 50, 50) ;}@ Override public void surfaceChanged (SurfaceHolder holder, int format, int width, int height) {}@ Override public void surfaceDestroyed (SurfaceHolder holder) {if (timer! = Null) {timer. cancel (); timer = null ;}} package com. example. test; import java. util. timer; import java. util. timerTask; import android. annotation. suppressLint; import android. content. context; import android. graphics. bitmap; import android. graphics. bitmapFactory; import android. graphics. canvas; import android. graphics. color; import android. graphics. matrix; import android. graphics. paint; import android. grap Hics. pixelFormat; import android. graphics. porterDuff. mode; import android. OS. handler; import android. OS. message; import android. util. log; import android. view. surfaceHolder; import android. view. surfaceView; import android. view. surfaceHolder. callback; @ SuppressLint ("HandlerLeak") class Surface extends SurfaceView implements Callback {Bitmap bmp; private Paint mPaint; private SurfaceHolder mHolder; public Surface (Context context) {super (context); mHolder = getHolder (); mHolder. addCallback (this); mPaint = new Paint (); mPaint. setColor (Color. GREEN); mPaint. setAntiAlias (true); // setFocusable (true); setFocusableInTouchMode (true); // setZOrderOnTop (true); // mHolder. setFormat (PixelFormat. TRANSPARENT); // set the background to TRANSPARENT bmp = BitmapFactory. decodeResource (getResources (), R. drawable. camera_r_local); bmp = Bitmap. createScaledB Itmap (bmp, 15, 15, false);} public Handler handler = new Handler () {@ Overridepublic void handleMessage (Message msg) {switch (msg. what) {case 0: canvas_ OK (); break;} super. handleMessage (msg) ;}}; public void canvas_ OK () {Canvas canvas = null; try {canvas = mHolder. lockCanvas (); canvas. drawColor (Color. TRANSPARENT, Mode. CLEAR); // CLEAR the screen // canvas. save (); Matrix matrix = new Matrix (); matrix. postTranslate (130, 0 ); Matrix. postRotate (degree, 130,130); canvas. drawBitmap (bmp, matrix, mPaint); // canvas. restore ();} catch (Exception e) {} finally {if (canvas! = Null) {mHolder. unlockCanvasAndPost (canvas) ;}} int degree = 0; Timer timer = new Timer (); boolean flag = true; @ Overridepublic void surfaceCreated (SurfaceHolder holder) {canvas_ OK (); timer. schedule (new TimerTask () {@ Overridepublic void run () {if (flag) {degree ++; if (degree = 360) {flag = false ;}} else {degree --; if (degree =-360 | degree = 0) {flag = true ;}} Log. e ("flag", degree + ":" + flag); handler. SendEmptyMessage (0) ;}}, 50, 50) ;}@ Overridepublic void surfaceChanged (SurfaceHolder holder, int format, int width, int height) {}@ Overridepublic void surfaceDestroyed (SurfaceHolder holder) {if (timer! = Null) {timer. cancel (); timer = null ;}}}

 

Main7.java is the main class

package com.example.test;    import android.app.Activity;  import android.os.Bundle;  import android.widget.RelativeLayout;    public class Main7 extends Activity{      Surface surface;      RelativeLayout.LayoutParams laParams;      @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          surface = new Surface(this);          laParams = new RelativeLayout.LayoutParams(260,  260);          setContentView(surface, laParams);      }    }  package com.example.test;import android.app.Activity;import android.os.Bundle;import android.widget.RelativeLayout;public class Main7 extends Activity{Surface surface;RelativeLayout.LayoutParams laParams;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);surface = new Surface(this);laParams = new RelativeLayout.LayoutParams(260,  260);setContentView(surface, laParams);}}

 

As follows: