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 = ;
     private RectF rectF = new RectF(,,,);
     private float sweepAngel = ;
     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();
         canvas.drawText("LogicView", rx, , paint);

         canvas.drawArc(rectF,,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 =  - paint.measureText("LogicView");
         }

         sweepAngel ++ ;

         if(sweepAngel > ){
             sweepAngel = ;
         }
         int r = rand.nextInt();
         int g = rand.nextInt();
         int b = rand.nextInt();
         paint.setARGB(, r, g, b);
     }

     class MyThread extends Thread{
         @Override
         public void run() {
             while(true){
                 logic();
                 postInvalidate();
                 try {
                     Thread.sleep();
                 } catch (InterruptedException e) {
                     e.printStackTrace();
                 }
             }

         }
     }

 }