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重要的是如何實現(xiàn)自定義的view效果

（1）創(chuàng)建類，繼承view，重寫onDraw和onMesure方法

public class CirclePercentBar extends View{

    private Context mContext;

    private int mArcColor;
    private int mArcWidth;
    private int mCenterTextColor;
    private int mCenterTextSize;
    private int mCircleRadius;
    private Paint arcPaint;
    private Paint arcCirclePaint;
    private Paint centerTextPaint;
    private RectF arcRectF;
    private Rect textBoundRect;
    private float mCurData=0;
    private int arcStartColor;
    private int arcEndColor;
    private Paint startCirclePaint;

    public CirclePercentBar(Context context) {
        this(context, null);
    }

    public CirclePercentBar(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CirclePercentBar(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mContext=context;
        TypedArray typedArray=context.obtainStyledAttributes(attrs,R.styleable.CirclePercentBar,defStyleAttr,0);
        mArcColor = typedArray.getColor(R.styleable.CirclePercentBar_arcColor,0xff0000);
        mArcWidth = typedArray.getDimensionPixelSize(R.styleable.CirclePercentBar_arcWidth, DisplayUtil.dp2px(context, 20));
        mCenterTextColor = typedArray.getColor(R.styleable.CirclePercentBar_centerTextColor, 0x0000ff);
        mCenterTextSize = typedArray.getDimensionPixelSize(R.styleable.CirclePercentBar_centerTextSize, DisplayUtil.dp2px(context, 20));
        mCircleRadius = typedArray.getDimensionPixelSize(R.styleable.CirclePercentBar_circleRadius, DisplayUtil.dp2px(context, 100));
        arcStartColor = typedArray.getColor(R.styleable.CirclePercentBar_arcStartColor,
                ContextCompat.getColor(mContext, R.color.green));
        arcEndColor = typedArray.getColor(R.styleable.CirclePercentBar_arcEndColor,
                ContextCompat.getColor(mContext, R.color.yellow));

        typedArray.recycle();

        initPaint();

    }

    private void initPaint() {

        startCirclePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        startCirclePaint.setStyle(Paint.Style.FILL);
        //startCirclePaint.setStrokeWidth(mArcWidth);
        startCirclePaint.setColor(arcStartColor);

        arcCirclePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        arcCirclePaint.setStyle(Paint.Style.STROKE);
        arcCirclePaint.setStrokeWidth(mArcWidth);
        arcCirclePaint.setColor(ContextCompat.getColor(mContext,R.color.colorAccent));
        arcCirclePaint.setStrokeCap(Paint.Cap.ROUND);

        arcPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        arcPaint.setStyle(Paint.Style.STROKE);
        arcPaint.setStrokeWidth(mArcWidth);
        arcPaint.setColor(mArcColor);
        arcPaint.setStrokeCap(Paint.Cap.ROUND);

        centerTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        centerTextPaint.setStyle(Paint.Style.STROKE);
        centerTextPaint.setColor(mCenterTextColor);
        centerTextPaint.setTextSize(mCenterTextSize);

        //圓弧的外接矩形
        arcRectF = new RectF();

        //文字的邊界矩形
        textBoundRect = new Rect();

    }


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        setMeasuredDimension(measureDimension(widthMeasureSpec),measureDimension(heightMeasureSpec));
    }

    private int measureDimension(int measureSpec) {
        int result;
        int specMode=MeasureSpec.getMode(measureSpec);
        int specSize=MeasureSpec.getSize(measureSpec);
        if(specMode==MeasureSpec.EXACTLY){
            result=specSize;
        }else{
            result=mCircleRadius*2;
            if(specMode==MeasureSpec.AT_MOST){
                result=Math.min(result,specSize);
            }
        }
        return result;
    }

    @Override
    protected void onDraw(Canvas canvas) {

        canvas.rotate(-90, getWidth()/ 2, getHeight()/ 2);

        arcRectF.set(getWidth()/2-mCircleRadius+mArcWidth/2,getHeight()/2-mCircleRadius+mArcWidth/2
                ,getWidth()/2+mCircleRadius-mArcWidth/2,getHeight()/2+mCircleRadius-mArcWidth/2);


        canvas.drawArc(arcRectF, 0,360,false,arcCirclePaint);

        arcPaint.setShader(new SweepGradient(getWidth()/2,getHeight()/2,arcStartColor,arcEndColor));
        canvas.drawArc(arcRectF, 0,360* mCurData /100,false,arcPaint);

        canvas.rotate(90, getWidth()/ 2, getHeight()/ 2);
        canvas.drawCircle(getWidth()/2,getHeight()/2-mCircleRadius+mArcWidth/2,mArcWidth/2,startCirclePaint);

        String data= String.valueOf(mCurData) +"%";
        centerTextPaint.getTextBounds(data,0,data.length(),textBoundRect);
        canvas.drawText(data,getWidth()/2-textBoundRect.width()/2,getHeight()/2+textBoundRect.height()/2,centerTextPaint);

    }

    public void setPercentData(float data, TimeInterpolator interpolator){
        ValueAnimator valueAnimator=ValueAnimator.ofFloat(mCurData,data);
        valueAnimator.setDuration((long) (Math.abs(mCurData-data)*30));
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator valueAnimator) {
                float value= (float) valueAnimator.getAnimatedValue();
                mCurData=(float)(Math.round(value*10))/10;
                invalidate();
            }
        });
        valueAnimator.setInterpolator(interpolator);
        valueAnimator.start();
    }
}

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（2）其中需要用到的類

public class DisplayUtil {
    public static int px2dp(Context context,float pxValue){
        final float scale=context.getResources().getDisplayMetrics().density;
        return (int)(pxValue/scale+0.5f);
    }
    public static int dp2px(Context context,float dpValue){
        final float scale=context.getResources().getDisplayMetrics().density;
        return (int)(dpValue*scale+0.5f);
    }
}

（3）attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="CirclePercentBar">
        <attr name="arcColor" format="color"/>
        <attr name="arcWidth" format="dimension"/>
        <attr name="centerTextColor" format="color"/>
        <attr name="centerTextSize" format="dimension"/>
        <attr name="circleRadius" format="dimension"/>
        <attr name="arcStartColor" format="color"/>
        <attr name="arcEndColor" format="color"/>
    </declare-styleable>
</resources>

（4）在activity_main里面寫布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
 
    <com.example.administrator.textc.CirclePercentBar
        android:id="@+id/circle_bar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:layout_gravity="center_horizontal"
        app:arcWidth="30dp"
        app:circleRadius="100dp"
        app:centerTextSize="30sp"
        app:arcColor="@color/colorPrimary"
        app:centerTextColor="@color/colorAccent"
        app:arcStartColor="@android:color/holo_green_light"/>

    <Button
        android:id="@+id/start_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="隨機"/>
</LinearLayout>

（6）編程實現(xiàn)效果：

public class MainActivity extends AppCompatActivity {
    CirclePercentBar circlePercentBar;
    Button startBtn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        circlePercentBar= (CirclePercentBar) findViewById(R.id.circle_bar);
        circlePercentBar.setPercentData(55.2f,new DecelerateInterpolator());

        startBtn= (Button) findViewById(R.id.start_btn);
        startBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                circlePercentBar.setPercentData((float) (100*Math.random()),new DecelerateInterpolator());
            }
        });
    }
}

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