<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:id="@+id/main_linlayout"
        android:layout_width="match_parent"
        android:layout_height="300dp"
        android:orientation="vertical">
    </LinearLayout>


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <Button
            android:id="@+id/bt"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="確定"/>
        <Button
            android:id="@+id/bt_clear"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="清空"/>
    </LinearLayout>

    <ImageView
        android:id="@+id/img"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="5dp"
        android:layout_gravity="center"/>
</LinearLayout>

package tester.ermu.com.handdrawdemo;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BlurMaskFilter;
import android.graphics.EmbossMaskFilter;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;


public class MainActivity extends Activity implements View.OnClickListener{
    EmbossMaskFilter emboss;
    BlurMaskFilter blur;
    DrawView drawView;
    private LinearLayout main_linlayout;
    private Button bt,bt_clear;
    private ImageView img;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init(); //初始化組件
        getWH();//獲取我們xml布局中view的寬高
    }

    //獲取我們xml布局中view的寬高
    private void getWH() {
        // 獲取創(chuàng)建的寬度和高度
        DisplayMetrics displayMetrics = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getRealMetrics(displayMetrics);
        // 創(chuàng)建一個DrawView，該DrawView的寬度、高度與該Activity保持相同
        main_linlayout = (LinearLayout)findViewById(R.id.main_linlayout);
        drawView = new DrawView(this, displayMetrics.widthPixels, displayMetrics.heightPixels);

        main_linlayout.addView(drawView);
        drawView.requestFocus();
    }

    private void init() {
        bt = (Button)findViewById(R.id.bt);
        bt.setOnClickListener(this);
        bt_clear = (Button)findViewById(R.id.bt_clear);
        bt_clear.setOnClickListener(this);

        img = (ImageView) findViewById(R.id.img);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.bt:
                Bitmap bit = drawView.getPaintBitmap();
                img .setImageBitmap(bit);
                break;

            case R.id.bt_clear:
                drawView.clear();

                break;
        }
    }
}

package tester.ermu.com.handdrawdemo;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class DrawView extends View {
    // 定義記錄前一個拖動事件發(fā)生點的坐標
    float preX;
    float preY;
    private Path path;
    public Paint paint = null;
    // 定義一個內存中的圖片，該圖片將作為緩沖區(qū)
    Bitmap cacheBitmap = null;
    // 定義cacheBitmap上的Canvas對象
    Canvas cacheCanvas = null;

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

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

    public DrawView(Context context, int width , int height) {
        super(context);
        // 創(chuàng)建一個與該View相同大小的緩存區(qū)
        cacheBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        cacheCanvas = new Canvas();
        path = new Path();
        // 設置cacheCanvas將會繪制到內存中的cacheBitmap上
        cacheCanvas.setBitmap(cacheBitmap);
        // 設置畫筆的顏色
        paint = new Paint(Paint.DITHER_FLAG);
        paint.setColor(Color.RED);
        // 設置畫筆風格
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(3);
        // 反鋸齒
        paint.setAntiAlias(true);
        paint.setDither(true);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event)
    {
        // 獲取拖動事件的發(fā)生位置
        float x = event.getX();
        float y = event.getY();
        switch (event.getAction())
        {
            case MotionEvent.ACTION_DOWN:
                // 從前一個點繪制到當前點之后，把當前點定義成下次繪制的前一個點
                path.moveTo(x, y);
                preX = x;
                preY = y;
                break;
            case MotionEvent.ACTION_MOVE:
                // 從前一個點繪制到當前點之后，把當前點定義成下次繪制的前一個點
                path.quadTo(preX, preY, x, y);
                preX = x;
                preY = y;
                break;
            case MotionEvent.ACTION_UP:
                cacheCanvas.drawPath(path, paint); // ①
                path.reset();
                break;
        }
        invalidate();
        // 返回true表明處理方法已經處理該事件
        return true;
    }
    @Override
    public void onDraw(Canvas canvas)
    {
        Paint bmpPaint = new Paint();
        // 將cacheBitmap繪制到該View組件上
        canvas.drawBitmap(cacheBitmap, 0, 0, bmpPaint); // ②
        // 沿著path繪制
        canvas.drawPath(path, paint);
    }

    //獲取我們繪制成功后的圖片

    public Bitmap getPaintBitmap() {
        return resizeImage(cacheBitmap, 620, 780);
    }



    // 縮放
    public static Bitmap resizeImage(Bitmap bitmap, int width, int height) {
        //獲取圖片的寬高
        int originWidth = bitmap.getWidth();
        int originHeight = bitmap.getHeight();

        //這里縮放我們的尺寸，縮放多少自己去定義
        float scaleWidth = ((float) width) / originWidth;
        float scaleHeight = ((float) height) / originHeight;

        //進行縮放
        Matrix matrix = new Matrix();
        matrix.postScale(scaleWidth, scaleHeight);
        Bitmap resizedBitmap = Bitmap.createBitmap(bitmap, 0, 0, originWidth,
                originHeight, matrix, true);
        return resizedBitmap;
    }


    //清除畫板
    public void clear() {
        if (cacheBitmap != null) {
            path.reset();
            cacheCanvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
            invalidate();
        }
    }
}