自定义View的编写

在项目的时候，很多情况要用到自定义View来达到自己想要的效果，所有自定义View的编写很重要。

首先看看所要实现的效果：

最上面的一行字“LogicView”每次从左向右滚动，下面的圆从角度0到360不断变化。并且颜色随机地变化。

MainActivity.java

package com.example.myview;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //setContentView(new Myview(this));
    }
}

activity_main.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >
    <com.example.myview.TestClass      
        android:layout_width="match_parent"
        android:layout_height="match_parent"
   
        />
</FrameLayout>

TestClass.java

package com.example.myview;

import java.util.Random;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.View;

public  class TestClass extends View{

    private MyThread thread;
    private Paint paint = new Paint();
    private float rx = 0;
    private RectF rectF = new RectF(0,60,100,160);
    private float sweepAngel = 0;
    Random rand = new Random();
    
    public TestClass(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public TestClass(Context context) {
        super(context);
    }
    
    private  void drawSub(Canvas canvas){
        paint.setTextSize(30);
        canvas.drawText("LogicView", rx, 30, paint);
        
        canvas.drawArc(rectF,0,sweepAngel,true,paint);
    }
    
    protected void onDraw(Canvas canvas){
        if(thread==null){
            thread = new MyThread();
            thread.start();
        }else{
            drawSub(canvas);
        }
    }
    
    private void logic(){
        rx++;
        if(rx > getWidth()){
            rx = 0 - paint.measureText("LogicView");
        }
        
        sweepAngel ++ ;
        
        if(sweepAngel > 360){
            sweepAngel = 0; 
        }
        int r = rand.nextInt(256);
        int g = rand.nextInt(256);
        int b = rand.nextInt(256);
        paint.setARGB(255, r, g, b);
    }
    
    class MyThread extends Thread{
        @Override
        public void run() {
            while(true){
                logic();
                postInvalidate();
                try {
                    Thread.sleep(30);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            
        }
    }
    
}