概念
- 画笔类:Paint用于指定颜色、透明度、笔触磅数、图形样式。
- 画布类:Canvas用于指定背景颜色,尺寸画笔的容器。
绘图的基本步骤
继承View类,重写OnDraw()——>在Activity中引用
案例绘制一个矩形
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/framelayout"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
</FrameLayout>
MyView.java
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.View;
public class MyView extends View {
public MyView(Context context) {
super(context);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint paint = new Paint(); //定义一个默认的画笔
paint.setColor(0xFFFF6600);
paint.setStyle(Paint.Style.FILL);//设置填充方式
canvas.drawRect
(10,10,280,150,paint);
//绘制矩形
}
}
MainActivity.java
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.FrameLayout;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FrameLayout frameLayout = findViewById(R.id.framelayout);
frameLayout.addView(new MyView(this));
}
}
效果: