自定义view

package com.bwei.cpm;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Matrix;import android.graphics.Paint;import android.graphics.Path;import android.graphics.PathMeasure;import android.util.AttributeSet;import android.view.View;/** * 1. 类的用途 * 2. @author forever * 3. @date 2017/9/4 13:52 */public class CustomView extends View {    //定义几个必要的变量    private float currentValue = 0;     // 用于纪录当前的位置,取值范围[0,1]映射Path的整个长度    private float[] pos;                // 当前点的实际位置    private float[] tan;                // 当前点的tangent值,用于计算图片所需旋转的角度    private Bitmap mBitmap;             // 箭头图片    private Matrix mMatrix;             // 矩阵,用于对图片进行一些操作    private int color;    private Paint paint;    private Paint mPaint;    public CustomView(Context context) {        super(context);        init(context);    }    public CustomView(Context context, AttributeSet attrs) {        super(context, attrs);        init(context);    }    public CustomView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init(context);        TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomView, defStyleAttr, 0);        int indexCount = typedArray.getIndexCount();        for (int i = 0; i < indexCount; i++) {            int attr = typedArray.getIndex(i);            switch (attr) {                case R.styleable.CustomView_viewColor:                    // 默认颜色设置,黑色                    color = typedArray.getColor(attr, Color.BLACK);                    break;            }        }        typedArray.recycle();        mPaint = new Paint();        mPaint.setColor(color);    }    // 初始化这些变量(在构造函数中调用这个方法):    private void init(Context context) {        pos = new float[2];        tan = new float[2];        BitmapFactory.Options options = new BitmapFactory.Options();        options.inSampleSize = 6;       // 缩放图片        mBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.jiantou2, options);        mMatrix = new Matrix();    }    //具体绘制:    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        paint = new Paint();        paint.setStyle(Paint.Style.STROKE);        paint.setStrokeWidth(5);        paint.setColor(color);        canvas.translate(60, 60);      // 平移坐标系        Path path = new Path();                                 // 创建 Path        path.addCircle(200, 200, 200, Path.Direction.CW);           // 添加一个圆形        PathMeasure measure = new PathMeasure(path, false);     // 创建 PathMeasure        currentValue += 0.005;                                  // 计算当前的位置在总长度上的比例[0,1]        if (currentValue >= 1) {            currentValue = 0;        }        //这个方法是用于得到路径上某一长度的位置以及该位置的正切值：        measure.getPosTan(measure.getLength() * currentValue, pos, tan);        // 获取当前位置的坐标以及趋势        mMatrix.reset();                                                        // 重置Matrix        float degrees = (float) (Math.atan2(tan[1], tan[0]) * 180.0 / Math.PI); // 计算图片旋转角度        mMatrix.postRotate(degrees, mBitmap.getWidth() / 2, mBitmap.getHeight() / 2);   // 旋转图片        mMatrix.postTranslate(pos[0] - mBitmap.getWidth() / 2, pos[1] - mBitmap.getHeight() / 2);   // 将图片绘制中心调整到与当前点重合        canvas.drawPath(path, paint);                                   // 绘制 Path        canvas.drawBitmap(mBitmap, mMatrix, paint);                     // 绘制箭头        invalidate();                                                           // 重绘页面    }    //改变颜色    public void setColor(int red) {        color = red;    }}//activity
package com.bwei.cpm;import android.graphics.Color;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.Button;import android.widget.Toast;public class MainActivity extends AppCompatActivity implements View.OnClickListener {    private Button change;    private Button up;    private Button down;    private CustomView myview;    private boolean isFly = true;    private int index = 10;    private Handler handler = new Handler() {        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            switch (msg.what) {                case 0: {                    myview.invalidate();                }                break;                case 1: {                    myview.invalidate();                }                break;            }        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initView();        //剪头开始移动        startFly(isFly);    }    private void startFly(final boolean isFly) {        new Thread(new Runnable() {            @Override            public void run() {                try {                    while (isFly) {                        if (index > 0) {                            Thread.sleep(index);                            handler.sendEmptyMessage(0);                        } else {                            Thread.sleep(10);                            handler.sendEmptyMessage(1);                        }                    }                } catch (InterruptedException e) {                    e.printStackTrace();                }            }        }).start();    }    private void initView() {        change = (Button) findViewById(R.id.change);        up = (Button) findViewById(R.id.up);        down = (Button) findViewById(R.id.down);        myview = (CustomView) findViewById(R.id.myview);        change.setOnClickListener(this);        up.setOnClickListener(this);        down.setOnClickListener(this);        myview.setColor(Color.BLACK);    }    @Override    public void onClick(View view) {        switch (view.getId()) {            case R.id.change:                myview.setColor(Color.RED);                break;            case R.id.up:                index = index - 10;                if (index <= 0) {                    Toast.makeText(MainActivity.this, "闪电般：" + index, Toast.LENGTH_SHORT).show();                }                break;            case R.id.down:                index = index + 10;                break;        }    }}

// 布局
<?xml version="1.0" encoding="utf-8"?><LinearLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    xmlns:tools="http://schemas.android.com/tools"    xmlns:app="http://schemas.android.com/apk/res-auto"    android:orientation="vertical"    >    <Button        android:id="@+id/change"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="改变颜色"        />    <Button        android:id="@+id/up"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="加速"        />    <Button        android:id="@+id/down"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="减速"        tools:layout_editor_absoluteY="0dp"        tools:layout_editor_absoluteX="8dp" />    <com.bwei.cpm.CustomView        android:id="@+id/myview"        android:layout_width="400dp"        android:layout_height="400dp"        app:viewColor="@android:color/black"        tools:layout_editor_absoluteY="0dp"        tools:layout_editor_absoluteX="0dp" /></LinearLayout>