自定义View

1.自定义View分类
2.时钟案例
3.圆形ImageView

View分类
ImageView

• ImageButton
• QuickContactBadge
• AppCompatImageView
  TextView
• EditText
• Button
• RadioButton
• ToggleButton
• CheckBox
• Switch
• TextClock
• Chronometer
• RowHeaderView

ViewGroup

• LinearLayout
• RelativeLayout
• ViewPager
• ListView
• AbsoulteLayout
• FrameLayout
• GridLayout

TextureView
ViewStub
Tabltem
Space

时钟案例
onDraw方法

 protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint paint=new Paint();
        paint.setColor(Color.RED);
        paint.setAntiAlias(true);
        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.watch);
        RectF rectF = new RectF(getWidth() / 4+20, getHeight() / 2 - getWidth() / 4+25, getWidth() / 4 * 3-25, getHeight() /2 + getHeight() / 8);
        canvas.drawBitmap(bitmap, null, rectF, paint);

表盘背景

 Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.watch);
        RectF rectF = new RectF(getWidth() / 4+20, getHeight() / 2 - getWidth() / 4+25, getWidth() / 4 * 3-25, getHeight() /2 + getHeight() / 8);
        canvas.drawBitmap(bitmap, null, rectF, paint);

时针

canvas.save();
        canvas.rotate(hours*30+minute*30/60,getWidth()/2,getHeight()/2);
        paint.setColor(Color.BLACK);
        paint.setStrokeWidth(5);
        canvas.drawLine(getWidth() / 2, getHeight() / 2, getWidth() / 2, getHeight() / 2 - getHeight() / 8 + 55, paint);
        canvas.restore();

分针

    canvas.save();
        canvas.rotate(minute*6,getWidth()/2,getHeight()/2);
        paint.setColor(Color.BLACK);
        paint.setStrokeWidth(3);
        canvas.drawLine(getWidth() / 2, getHeight() / 2, getWidth() / 2 + 12, getHeight() / 2 - getHeight() / 8 + 40, paint);
        canvas.restore();

秒针

canvas.save();
canvas.rotate(second*6,getWidth()/2,getHeight()/2);
paint.setColor(Color.BLACK);
paint.setStrokeWidth(1);
        canvas.drawLine(getWidth() / 2, getHeight() / 2, getWidth() / 2 + 15, getHeight() / 2 - getHeight() / 8 + 20, paint);
        canvas.restore();

完整代码

package com.example.a17708.pratice;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.os.Build;
import android.support.annotation.Nullable;
import android.support.annotation.RequiresApi;
import android.util.AttributeSet;
import android.view.View;

public class MyView extends View {
    private int hours=20;
    private int minute=20;
    private int second=0;

    public MyView(Context context) {
        super(context);
    }

    public MyView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public MyView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public MyView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint paint=new Paint();
        paint.setColor(Color.RED);
        paint.setAntiAlias(true);
        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.watch);
        RectF rectF = new RectF(getWidth() / 4+20, getHeight() / 2 - getWidth() / 4+25, getWidth() / 4 * 3-25, getHeight() /2 + getHeight() / 8);
        canvas.drawBitmap(bitmap, null, rectF, paint);
//画直线（时针）
        canvas.save();
        canvas.rotate(hours*30+minute*30/60,getWidth()/2,getHeight()/2);
        paint.setColor(Color.BLACK);
        paint.setStrokeWidth(5);
        canvas.drawLine(getWidth() / 2, getHeight() / 2, getWidth() / 2, getHeight() / 2 - getHeight() / 8 + 55, paint);
        canvas.restore();
//画直线（分针）
        canvas.save();
        canvas.rotate(minute*6,getWidth()/2,getHeight()/2);
        paint.setColor(Color.BLACK);
        paint.setStrokeWidth(3);
        canvas.drawLine(getWidth() / 2, getHeight() / 2, getWidth() / 2 + 12, getHeight() / 2 - getHeight() / 8 + 40, paint);
        canvas.restore();
//画直线（秒针）
canvas.save();
canvas.rotate(second*6,getWidth()/2,getHeight()/2);
paint.setColor(Color.BLACK);
paint.setStrokeWidth(1);
        canvas.drawLine(getWidth() / 2, getHeight() / 2, getWidth() / 2 + 15, getHeight() / 2 - getHeight() / 8 + 20, paint);
        canvas.restore();
for(int i=0;i<=60;i++){
    canvas.save();
    canvas.rotate(6*i,getWidth()/2,getHeight()/2);
    paint.setStrokeWidth(2);
    if(i%5==0){
        paint.setStrokeWidth(8);
        canvas.drawLine(getWidth() / 2, getHeight() / 2 - getHeight() / 8 + 20, getWidth() / 2, getHeight() / 2 - getWidth() / 4 + 35, paint);
    } else {
        paint.setStrokeWidth(4);
        canvas.drawLine(getWidth() / 2, getHeight() / 2 - getHeight() / 8 + 20, getWidth() / 2, getHeight() / 2 - getWidth() / 4+40, paint);

    }
    canvas.restore();
}

    }

    public void refresh(int h, int m, int s) {
        this.hours = h;
        this.minute = m;
        this.second = s;
        invalidate();//再次触发onDraw方法
    }
}

package com.example.a17708.pratice;

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import java.util.Calendar;

public class MyViewActivity extends AppCompatActivity {
    private MyView myView;
    private int hours;
    private int minute;
    private int second;
    private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            myView.refresh(msg.what, msg.arg1, msg.arg2);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_view);

        myView = findViewById(R.id.my_view);

        Calendar calendar = Calendar.getInstance();
        hours = calendar.get(Calendar.HOUR_OF_DAY);
        minute = calendar.get(Calendar.MINUTE);
        second = calendar.get(Calendar.SECOND);

        myView.refresh(hours, minute, second);

        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    second++;
                    if (second == 60) {
                        second = 0;
                        minute++;
                    }
                    try {
                        Message message = handler.obtainMessage();
                        message.what = hours;
                        message.arg1 = minute;
                        message.arg2 = second;
                        handler.sendMessage(message);
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }
}

圆形ImageView

package com.example.a17708.pratice;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Shader;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.ImageView;


@SuppressLint("AppCompatCustomView")
public class MyImageView extends ImageView {
    private Paint mPaint; //画笔

    private int mRadius; //圆形图片的半径

    private float mScale; //图片的缩放比例
    public MyImageView(Context context) {
        super(context);
    }

    public MyImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public MyImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int size = Math.min(getMeasuredWidth(), getMeasuredHeight());
        mRadius = size / 2;

        setMeasuredDimension(size, size);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        mPaint = new Paint();
        Bitmap bitmap = drawableToBitmap(getDrawable());

        //初始化BitmapShader，传入bitmap对象
        BitmapShader bitmapShader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

        //计算缩放比例
        mScale = (mRadius * 2.0f) / Math.min(bitmap.getHeight(), bitmap.getWidth());

        Matrix matrix = new Matrix();
        matrix.setScale(mScale, mScale);
        bitmapShader.setLocalMatrix(matrix);


        mPaint.setShader(bitmapShader);

        //画圆形，指定好中心点坐标、半径、画笔
        canvas.drawCircle(mRadius, mRadius, mRadius, mPaint);
    }

    //写一个drawble转BitMap的方法
    private Bitmap drawableToBitmap(Drawable drawable) {
        if (drawable instanceof BitmapDrawable) {
            BitmapDrawable bd = (BitmapDrawable) drawable;
            return bd.getBitmap();
        }
        int w = drawable.getIntrinsicWidth();
        int h = drawable.getIntrinsicHeight();
        Bitmap bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        drawable.setBounds(0, 0, w, h);
        drawable.draw(canvas);
        return bitmap;

    }

}