Android 手繪 - 支持保存為圖片

畫了一個非常難看的機器人。。。

附上關鍵代碼：

MainView.java

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package com.tszy.views;
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import java.io.File;
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import java.io.FileNotFoundException;
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import java.io.FileOutputStream;
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import java.io.IOException;
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import android.content.Context;
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import android.graphics.Bitmap;
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import android.graphics.Bitmap.CompressFormat;
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import android.graphics.Bitmap.Config;
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import android.graphics.Canvas;
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import android.graphics.Color;
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import android.graphics.Paint;
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import android.graphics.Path;
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import android.util.AttributeSet;
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import android.view.MotionEvent;
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import android.view.View;
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public class MainView extends View {
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    private Paint paint;
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    private Canvas cacheCanvas;
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    private Bitmap cachebBitmap;
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    private Path path;
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    private int clr_bg, clr_fg;
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    public MainView(Context context, AttributeSet attrs) {
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        super(context, attrs);
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        clr_bg = Color.WHITE;
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        clr_fg = Color.CYAN;
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        paint = new Paint();
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        paint.setAntiAlias(true); // 抗鋸齒
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        paint.setStrokeWidth(3); // 線條寬度
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        paint.setStyle(Paint.Style.STROKE); // 畫輪廓
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        paint.setColor(clr_fg); // 顏色
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        path = new Path();
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        // 創建一張屏幕大小的位圖，作為緩沖
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        cachebBitmap = Bitmap.createBitmap(480, 800, Config.ARGB_8888);
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        cacheCanvas = new Canvas(cachebBitmap);
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        cacheCanvas.drawColor(clr_bg);
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    }
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    public MainView(Context context) {
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        super(context);
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    }
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    @Override
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    protected void onDraw(Canvas canvas) {
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        canvas.drawColor(clr_bg);
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        // 繪制上一次的，否則不連貫
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        canvas.drawBitmap(cachebBitmap, 0, 0, null);
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        canvas.drawPath(path, paint);     
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    }
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    /**
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     * 清空畫布
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     */
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    public void clear() {
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        path.reset();
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        cacheCanvas.drawColor(clr_bg);
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        invalidate();
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    }
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    /**
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     * 將畫布的內容保存到文件
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     * @param filename
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     * @throws FileNotFoundException
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     */
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    public void saveToFile(String filename) throws FileNotFoundException {
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        File f = new File(filename);
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        if(f.exists())
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            throw new RuntimeException("文件：" + filename + " 已存在！");
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        FileOutputStream fos = new FileOutputStream(new File(filename));
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        //將 bitmap 壓縮成其他格式的圖片數據
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        cachebBitmap.compress(CompressFormat.PNG, 50, fos);
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        try {
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            fos.close();
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        } catch (IOException e) {
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            // TODO Auto-generated catch block
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            e.printStackTrace();
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        }
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    }
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    private float cur_x, cur_y;
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    private boolean isMoving;
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    @Override
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    public boolean onTouchEvent(MotionEvent event) {
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        // TODO Auto-generated method stub
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        float x = event.getX();
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        float y = event.getY();
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        switch (event.getAction()) {
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            case MotionEvent.ACTION_DOWN : {
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                cur_x = x;
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                cur_y = y;
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                path.moveTo(cur_x, cur_y);
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                isMoving = true;
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                break;
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            }
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            case MotionEvent.ACTION_MOVE : {
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                if (!isMoving)
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                    break;
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                // 二次曲線方式繪制
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                path.quadTo(cur_x, cur_y, x, y);
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                // 下面這個方法貌似跟上面一樣
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                // path.lineTo(x, y);
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                cur_x = x;
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                cur_y = y;
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                break;
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            }
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            case MotionEvent.ACTION_UP : {
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                // 鼠標彈起保存最後狀態
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                cacheCanvas.drawPath(path, paint);
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                path.reset();
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                isMoving = false;
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                break;
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            }
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        }
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        // 通知刷新界面
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        invalidate();
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        return true;
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    }
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}
Activity 代碼：

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@Override
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    public void onClick(View v) {
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        // TODO Auto-generated method stub
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        switch (v.getId()) {
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            case R.id.iv_btn_clear :
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                view.clear();
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                break;
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            case R.id.iv_btn_save : {
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                try {
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                    String sdState = Environment.getExternalStorageState(); // 判斷sd卡是否存在
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                    // 檢查SD卡是否可用
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                    if (!sdState.equals(android.os.Environment.MEDIA_MOUNTED)) {
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                        Toast.makeText(this, "SD卡未准備好！", Toast.LENGTH_SHORT).show();
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                        break;
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                    }
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                    //獲取系統圖片存儲路徑
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                    File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
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                    // Make sure the Pictures directory exists.
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                    path.mkdirs();
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                    //根據當前時間生成圖片名稱
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                    Calendar c = Calendar.getInstance();
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                    String name = ""
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                            + c.get(Calendar.YEAR) + c.get(Calendar.MONTH) + c.get(Calendar.DAY_OF_MONTH)
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                            + c.get(Calendar.HOUR_OF_DAY) + c.get(Calendar.MINUTE) + c.get(Calendar.SECOND)
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                             + ".png";
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                    //合成完整路徑，注意 / 分隔符
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                    String string = path.getPath() + "/" + name;
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                    view.saveToFile(string);
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                    Toast.makeText(this, "保存成功！\n文件保存在：" + string, Toast.LENGTH_LONG).show();
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                } catch (FileNotFoundException e) {
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                    Toast.makeText(this, "保存失敗！\n" + e, Toast.LENGTH_LONG).show();
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                }
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                break;
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            }
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        }
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    }
沒什麼難度，主要是將Bitmap轉PNG圖片那裡，找了一會發現 Canvas 沒有直接或間接保存的方法，剛好這裡我使用了雙緩沖，另一塊畫布的內容位圖自己創建的，很自然想到將這個畫布的位圖保存為文件即可。

再查看 Bitmap 有個 compress(CompressFormat format, int quality,OutputStream stream) 方法，很明顯將文件輸出流傳給這個方法就OK