Android 触摸画圈
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原文地址: http://stackoverflow.com/questions/11796357/
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时间：2020-08-20 08:54:28 来源:igfitidea点击:
Draw Circle on touch
提问by Code_Life
I am trying to draw a circle where user touches screen .
我正在尝试绘制一个用户触摸屏幕的圆圈。
public class MainActivity extends Activity implements OnTouchListener {
LinearLayout layout;
float x=0;
float y=0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_main);
layout=(LinearLayout)findViewById(R.id.layout);
layout.addView(new CustomView(MainActivity.this));
}
public class CustomView extends View {
Bitmap mBitmap;
Paint paint;
public CustomView(Context context) {
super(context);
mBitmap = Bitmap.createBitmap(400, 800, Bitmap.Config.ARGB_8888);
paint=new Paint();
paint.setColor(Color.RED);
paint.setStyle(Style.FILL);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.setBitmap(mBitmap);
canvas.drawCircle(x, y, 50, paint);
Toast.makeText(MainActivity.this, "DDD", 1).show();
}
}
@Override
public boolean onTouch(View v, MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
layout.invalidate();
}
return false;
}}
回答by sdabet
I would do it this way:
我会这样做：
public class TestActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new DrawingView(this));
}
class DrawingView extends SurfaceView {
private final SurfaceHolder surfaceHolder;
private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
public DrawingView(Context context) {
super(context);
surfaceHolder = getHolder();
paint.setColor(Color.RED);
paint.setStyle(Style.FILL);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if(event.getAction() == MotionEvent.ACTION_DOWN) {
if (surfaceHolder.getSurface().isValid()) {
Canvas canvas = surfaceHolder.lockCanvas();
canvas.drawColor(Color.BLACK);
canvas.drawCircle(event.getX(), event.getY(), 50, paint);
surfaceHolder.unlockCanvasAndPost(canvas);
}
}
return false;
}
}
}
回答by sdabet
The is your version with fixes to make it work:
这是您的版本，并进行了修复以使其正常工作：
public class MainActivity extends Activity {
LinearLayout layout;
float x = 0;
float y = 0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
layout=(LinearLayout)findViewById(R.id.layout);
layout.addView(new CustomView(MainActivity.this));
}
public class CustomView extends View {
Bitmap mBitmap;
Paint paint;
public CustomView(Context context) {
super(context);
mBitmap = Bitmap.createBitmap(400, 800, Bitmap.Config.ARGB_8888);
paint = new Paint();
paint.setColor(Color.RED);
paint.setStyle(Style.FILL);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawCircle(x, y, 50, paint);
}
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
x = event.getX();
y = event.getY();
invalidate();
}
return false;
}
}
}
