Android 实现一个简单的画板功能

程序员文章站 2022-05-31 11:51:32

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Android炫酷画板下载地址：源码1 源码2

一.效果图：

Android 实现一个简单的画板功能

二.快速实现：

a.支持撤销（undo）

b.支持反撤销（redo）

c.支持橡皮擦（eraser）

d.支持清除功能（clear）

e.支持保存为图像（save）

1.主函数代码：

import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity implements View.OnClickListener, PaletteView.Callback,Handler.Callback {

    private View mUndoView;
    private View mRedoView;
    private View mPenView;
    private View mEraserView;
    private View mClearView;
    private PaletteView mPaletteView;
    private ProgressDialog mSaveProgressDlg;
    private static final int MSG_SAVE_SUCCESS = 1;
    private static final int MSG_SAVE_FAILED = 2;
    private Handler mHandler;

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

        mPaletteView = (PaletteView) findViewById(R.id.palette);
        mPaletteView.setCallback(this);

        mUndoView = findViewById(R.id.undo);
        mRedoView = findViewById(R.id.redo);
        mPenView = findViewById(R.id.pen);
        mPenView.setSelected(true);
        mEraserView = findViewById(R.id.eraser);
        mClearView = findViewById(R.id.clear);

        mUndoView.setOnClickListener(this);
        mRedoView.setOnClickListener(this);
        mPenView.setOnClickListener(this);
        mEraserView.setOnClickListener(this);
        mClearView.setOnClickListener(this);

        mUndoView.setEnabled(false);
        mRedoView.setEnabled(false);

        mHandler = new Handler(this);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mHandler.removeMessages(MSG_SAVE_FAILED);
        mHandler.removeMessages(MSG_SAVE_SUCCESS);
    }

    private void initSaveProgressDlg(){
        mSaveProgressDlg = new ProgressDialog(this);
        mSaveProgressDlg.setMessage("正在保存,请稍候...");
        mSaveProgressDlg.setCancelable(false);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean handleMessage(Message msg) {
        switch (msg.what){
            case MSG_SAVE_FAILED:
                mSaveProgressDlg.dismiss();
                Toast.makeText(this,"保存失败",Toast.LENGTH_SHORT).show();
                break;
            case MSG_SAVE_SUCCESS:
                mSaveProgressDlg.dismiss();
                Toast.makeText(this,"画板已保存",Toast.LENGTH_SHORT).show();
                break;
        }
        return true;
    }

    private static void scanFile(Context context, String filePath) {
        Intent scanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
        scanIntent.setData(Uri.fromFile(new File(filePath)));
        context.sendBroadcast(scanIntent);
    }

    private static String saveImage(Bitmap bmp, int quality) {
        if (bmp == null) {
            return null;
        }
        File appDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
        if (appDir == null) {
            return null;
        }
        String fileName = System.currentTimeMillis() + ".jpg";
        File file = new File(appDir, fileName);
        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(file);
            bmp.compress(Bitmap.CompressFormat.JPEG, quality, fos);
            fos.flush();
            return file.getAbsolutePath();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.save:
                if(mSaveProgressDlg==null){
                    initSaveProgressDlg();
                }
                mSaveProgressDlg.show();
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        Bitmap bm = mPaletteView.buildBitmap();
                        String savedFile = saveImage(bm, 100);
                        if (savedFile != null) {
                            scanFile(MainActivity.this, savedFile);
                            mHandler.obtainMessage(MSG_SAVE_SUCCESS).sendToTarget();
                        }else{
                            mHandler.obtainMessage(MSG_SAVE_FAILED).sendToTarget();
                        }
                    }
                }).start();
                break;
        }
        return true;
    }

    @Override
    public void onUndoRedoStatusChanged() {
        mUndoView.setEnabled(mPaletteView.canUndo());
        mRedoView.setEnabled(mPaletteView.canRedo());
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.undo:
                mPaletteView.undo();
                break;
            case R.id.redo:
                mPaletteView.redo();
                break;
            case R.id.pen:
                v.setSelected(true);
                mEraserView.setSelected(false);
                mPaletteView.setMode(PaletteView.Mode.DRAW);
                break;
            case R.id.eraser:
                v.setSelected(true);
                mPenView.setSelected(false);
                mPaletteView.setMode(PaletteView.Mode.ERASER);
                break;
            case R.id.clear:
                mPaletteView.clear();
                break;
        }
    }
}

2.主要的自定义代码：

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Xfermode;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

import java.util.ArrayList;
import java.util.List;

/**
 * 自定义画板
 */
public class PaletteView extends View {

    private Paint mPaint;
    private Path mPath;
    private float mLastX;
    private float mLastY;
    private Bitmap mBufferBitmap;
    private Canvas mBufferCanvas;

    private static final int MAX_CACHE_STEP = 20;

    private List<DrawingInfo> mDrawingList;
    private List<DrawingInfo> mRemovedList;

    private Xfermode mXferModeClear;
    private Xfermode mXferModeDraw;
    private int mDrawSize;
    private int mEraserSize;
    private int mPenAlpha = 255;

    private boolean mCanEraser;

    private Callback mCallback;

    public enum Mode {
        DRAW,
        ERASER
    }

    private Mode mMode = Mode.DRAW;


    public PaletteView(Context context) {
        super(context);
        init();
    }

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

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

    public interface Callback {
        void onUndoRedoStatusChanged();
    }

    public void setCallback(Callback callback){
        mCallback = callback;
    }

    private void init() {
        setDrawingCacheEnabled(true);
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setFilterBitmap(true);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mDrawSize = DimenUtils.dp2pxInt(3);
        mEraserSize = DimenUtils.dp2pxInt(30);
        mPaint.setStrokeWidth(mDrawSize);
//        mPaint.setColor(0XFF000000);//设置画笔的颜色
        mPaint.setColor(Color.BLUE);
        mXferModeDraw = new PorterDuffXfermode(PorterDuff.Mode.SRC);
        mXferModeClear = new PorterDuffXfermode(PorterDuff.Mode.CLEAR);
        mPaint.setXfermode(mXferModeDraw);
    }

    private void initBuffer(){
        mBufferBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
        mBufferCanvas = new Canvas(mBufferBitmap);
    }

    private abstract static class DrawingInfo {
        Paint paint;
        abstract void draw(Canvas canvas);
    }

    private static class PathDrawingInfo extends DrawingInfo{

        Path path;

        @Override
        void draw(Canvas canvas) {
            canvas.drawPath(path, paint);
        }
    }

    public Mode getMode() {
        return mMode;
    }

    public void setMode(Mode mode) {
        if (mode != mMode) {
            mMode = mode;
            if (mMode == Mode.DRAW) {
                mPaint.setXfermode(mXferModeDraw);
                mPaint.setStrokeWidth(mDrawSize);
            } else {
                mPaint.setXfermode(mXferModeClear);
                mPaint.setStrokeWidth(mEraserSize);
            }
        }
    }

    public void setEraserSize(int size) {
        mEraserSize = size;
    }

    public void setPenRawSize(int size) {
        mDrawSize = size;
        if(mMode == Mode.DRAW){
            mPaint.setStrokeWidth(mDrawSize);
        }
    }

    public void setPenColor(int color) {
        mPaint.setColor(color);
    }

    private void reDraw(){
        if (mDrawingList != null) {
            mBufferBitmap.eraseColor(Color.TRANSPARENT);
            for (DrawingInfo drawingInfo : mDrawingList) {
                drawingInfo.draw(mBufferCanvas);
            }
            invalidate();
        }
    }

    public int getPenColor(){
        return mPaint.getColor();
    }

    public int getPenSize(){
        return mDrawSize;
    }

    public int getEraserSize(){
        return mEraserSize;
    }

    public void setPenAlpha(int alpha){
        mPenAlpha = alpha;
        if(mMode == Mode.DRAW){
            mPaint.setAlpha(alpha);
        }
    }

    public int getPenAlpha(){
        return mPenAlpha;
    }

    public boolean canRedo() {
        return mRemovedList != null && mRemovedList.size() > 0;
    }

    public boolean canUndo(){
        return mDrawingList != null && mDrawingList.size() > 0;
    }

    public void redo() {
        int size = mRemovedList == null ? 0 : mRemovedList.size();
        if (size > 0) {
            DrawingInfo info = mRemovedList.remove(size - 1);
            mDrawingList.add(info);
            mCanEraser = true;
            reDraw();
            if (mCallback != null) {
                mCallback.onUndoRedoStatusChanged();
            }
        }
    }

    public void undo() {
        int size = mDrawingList == null ? 0 : mDrawingList.size();
        if (size > 0) {
            DrawingInfo info = mDrawingList.remove(size - 1);
            if (mRemovedList == null) {
                mRemovedList = new ArrayList<>(MAX_CACHE_STEP);
            }
            if (size == 1) {
                mCanEraser = false;
            }
            mRemovedList.add(info);
            reDraw();
            if (mCallback != null) {
                mCallback.onUndoRedoStatusChanged();
            }
        }
    }

    public void clear() {
        if (mBufferBitmap != null) {
            if (mDrawingList != null) {
                mDrawingList.clear();
            }
            if (mRemovedList != null) {
                mRemovedList.clear();
            }
            mCanEraser = false;
            mBufferBitmap.eraseColor(Color.TRANSPARENT);
            invalidate();
            if (mCallback != null) {
                mCallback.onUndoRedoStatusChanged();
            }
        }
    }

    public Bitmap buildBitmap() {
        Bitmap bm = getDrawingCache();
        Bitmap result = Bitmap.createBitmap(bm);
        destroyDrawingCache();
        return result;
    }

    private void saveDrawingPath(){
        if (mDrawingList == null) {
            mDrawingList = new ArrayList<>(MAX_CACHE_STEP);
        } else if (mDrawingList.size() == MAX_CACHE_STEP) {
            mDrawingList.remove(0);
        }
        Path cachePath = new Path(mPath);
        Paint cachePaint = new Paint(mPaint);
        PathDrawingInfo info = new PathDrawingInfo();
        info.path = cachePath;
        info.paint = cachePaint;
        mDrawingList.add(info);
        mCanEraser = true;
        if (mCallback != null) {
            mCallback.onUndoRedoStatusChanged();
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (mBufferBitmap != null) {
            canvas.drawBitmap(mBufferBitmap, 0, 0, null);
        }
    }

    @SuppressWarnings("all")
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if(!isEnabled()){
            return false;
        }
        final int action = event.getAction() & MotionEvent.ACTION_MASK;
        final float x = event.getX();
        final float y = event.getY();
        switch (action) {
            case MotionEvent.ACTION_DOWN:
                mLastX = x;
                mLastY = y;
                if (mPath == null) {
                    mPath = new Path();
                }
                mPath.moveTo(x,y);
                break;
            case MotionEvent.ACTION_MOVE:
                //这里终点设为两点的中心点的目的在于使绘制的曲线更平滑，如果终点直接设置为x,y，效果和lineto是一样的,实际是折线效果
                mPath.quadTo(mLastX, mLastY, (x + mLastX) / 2, (y + mLastY) / 2);
                if (mBufferBitmap == null) {
                    initBuffer();
                }
                if (mMode == Mode.ERASER && !mCanEraser) {
                    break;
                }
                mBufferCanvas.drawPath(mPath,mPaint);
                invalidate();
                mLastX = x;
                mLastY = y;
                break;
            case MotionEvent.ACTION_UP:
                if (mMode == Mode.DRAW || mCanEraser) {
                    saveDrawingPath();
                }
                mPath.reset();
                break;
        }
        return true;
    }
}

3.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"
    android:orientation="vertical"
   >

    <com.beyondsw.palette.PaletteView
        android:id="@+id/palette"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:background="@drawable/bg"
        />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="56dp"
        android:orientation="horizontal"
        android:gravity="center"
        >
        <ImageView
            android:id="@+id/undo"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:scaleType="centerInside"
            android:src="@drawable/undo"
            android:background="@drawable/toolbar_item_bg"
            />
        <ImageView
            android:id="@+id/redo"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:scaleType="centerInside"
            android:src="@drawable/redo"
            android:background="@drawable/toolbar_item_bg"
            />
        <ImageView
            android:id="@+id/pen"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:scaleType="centerInside"
            android:layout_weight="1"
            android:src="@drawable/pen"
            android:background="@drawable/toolbar_item_bg"
            />
        <ImageView
            android:id="@+id/eraser"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:scaleType="centerInside"
            android:layout_weight="1"
            android:src="@drawable/eraser"
            android:background="@drawable/toolbar_item_bg"
            />
        <ImageView
            android:id="@+id/clear"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:scaleType="centerInside"
            android:src="@drawable/clear"
            android:background="@drawable/toolbar_item_bg"
            />
    </LinearLayout>
</LinearLayout>

4.按钮背景状态：（从左到右）

第一个按钮和第二个按钮背景一样

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
    <item android:state_pressed="true" android:drawable="@drawable/toolbar_bg"/>
    <item android:state_selected="true" android:drawable="@drawable/toolbar_bg"/>
    <item android:drawable="@android:color/transparent"/>
</selector>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
    <item android:state_pressed="true" android:drawable="@drawable/toolbar_bg"/>
    <item android:state_selected="true" android:drawable="@drawable/toolbar_bg"/>
    <item android:drawable="@android:color/transparent"/>
</selector>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
    <item android:state_pressed="true" android:drawable="@drawable/toolbar_bg"/>
    <item android:state_selected="true" android:drawable="@drawable/toolbar_bg"/>
    <item android:drawable="@android:color/transparent"/>
</selector>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
    <item android:state_pressed="true" android:drawable="@drawable/toolbar_bg"/>
    <item android:state_selected="true" android:drawable="@drawable/toolbar_bg"/>
    <item android:drawable="@android:color/transparent"/>
</selector>

5.工具类：

package com.beyondsw.palette;

import android.content.res.Resources;
import android.util.DisplayMetrics;
import android.util.TypedValue;

/**
 * 工具类转换
 */
public class DimenUtils {

    private static final Resources sResource = Resources.getSystem();

    public static float dp2px(float dp) {
        DisplayMetrics dm = sResource.getDisplayMetrics();
        return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, dm);
    }

    public static int dp2pxInt(float dp) {
        return (int) dp2px( dp);
    }

    public static float sp2px(float sp) {
        DisplayMetrics dm = sResource.getDisplayMetrics();
        return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, sp, dm);
    }

    public static int sp2pxInt(float sp) {
        return (int) sp2px(sp);
    }


}

参考：https://github.com/wensefu/android-palette

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