如何使用java for android在Canvas上画一个圆圈
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how to draw a circle on Canvas using java for android
提问by Hossein Dolatabadi
I want to draw a circle on a canvas in my android app. I searched a lot and realized if I need a dynamic form of painting which can be updated time by time I need to use canvas instead of imageView.
我想在我的 android 应用程序的画布上画一个圆圈。我搜索了很多并意识到我是否需要一种动态的绘画形式，它可以随时间更新，我需要使用画布而不是 imageView。
any help is appreciated
任何帮助表示赞赏
this is the code that I wrote so far but it will not draw anything on the android device screen:
这是我到目前为止编写的代码，但它不会在 android 设备屏幕上绘制任何内容：
private void createBitMap() {
Bitmap bitMap = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888); //creates bmp
bitMap = bitMap.copy(bitMap.getConfig(), true); //lets bmp to be mutable
Canvas canvas = new Canvas(bitMap); //draw a canvas in defined bmp
Paint paint = new Paint(); //define paint and paint color
paint.setColor(Color.RED);
paint.setStyle(Style.FILL_AND_STROKE);
//paint.setAntiAlias(true);
canvas.drawCircle(50, 50, 10, paint);
}
采纳答案by Jitender Dev
Update your createBitMapmethod like this
像这样更新你的createBitMap方法
private void createBitMap() {
// Create a mutable bitmap
Bitmap bitMap = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
bitMap = bitMap.copy(bitMap.getConfig(), true);
// Construct a canvas with the specified bitmap to draw into
Canvas canvas = new Canvas(bitMap);
// Create a new paint with default settings.
Paint paint = new Paint();
// smooths out the edges of what is being drawn
paint.setAntiAlias(true);
// set color
paint.setColor(Color.BLACK);
// set style
paint.setStyle(Paint.Style.STROKE);
// set stroke
paint.setStrokeWidth(4.5f);
// draw circle with radius 30
canvas.drawCircle(50, 50, 30, paint);
// set on ImageView or any other view
imageView.setImageBitmap(bitMap);
}
回答by Nambi
try this
尝试这个
create ImageView and use image.setImageBitmap(bitMap);to make a bitmap to visible.
创建 ImageView 并用于image.setImageBitmap(bitMap);使位图可见。
public class MainActivity extends Activity { ImageView image;
公共类 MainActivity 扩展 Activity { ImageView 图像；
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
image=(ImageView)findViewById(R.id.imageView1);
createBitMap();
}
private void createBitMap() {
Bitmap bitMap = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888); //creates bmp
bitMap = bitMap.copy(bitMap.getConfig(), true); //lets bmp to be mutable
Canvas canvas = new Canvas(bitMap); //draw a canvas in defined bmp
Paint paint = new Paint();
// smooths
paint.setAntiAlias(true);
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(4.5f);
// opacity
//p.setAlpha(0x80); //
canvas.drawCircle(50, 50, 30, paint);
image.setImageBitmap(bitMap);
}
