Android实现手写板和涂鸦功能

下面仿一个Android手写板和涂鸦的功能，直接上代码：

write_pad.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:greendroid="http://schemas.android.com/apk/res/com.cyrilmottier.android.gdcatalog"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <FrameLayout
        android:id="@+id/tablet_view"
        android:layout_width="fill_parent"
        android:layout_height="300dp" >
    </FrameLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@android:drawable/bottom_bar"
        android:paddingTop="4dp" >

        <Button
            android:id="@+id/write_pad_ok"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="确定" />

        <Button
            android:id="@+id/write_pad_clear"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="清除" />

        <Button
            android:id="@+id/write_pad_cancel"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="取消" />
    </LinearLayout>

</LinearLayout>

这个是手写板的主要布局文件，能够手写的部分是一个FrameLayout。下面有确定、清除和取消按钮，用来保存和擦除签名。

主要代码逻辑如下：

MainActivity.java

package com.jackie.handwriting;

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

import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends Activity {
  private ImageView mIVSign;
  private TextView mTVSign;
  private Bitmap mSignBitmap;

  /** Called when the activity is first created. */

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

    mIVSign = (ImageView) findViewById(R.id.iv_sign);
    mTVSign = (TextView) findViewById(R.id.tv_sign);

    mTVSign.setOnClickListener(new OnClickListener() {

      @Override
      public void onClick(View view) {
        WritePadDialog mWritePadDialog = new WritePadDialog(
            MainActivity.this, new WriteDialogListener() {

              @Override
              public void onPaintDone(Object object) {
                mSignBitmap = (Bitmap) object;
                createSignFile();
                mIVSign.setImageBitmap(mSignBitmap);
                mTVSign.setVisibility(View.GONE);
              }
            });

        mWritePadDialog.show();
      }
    });
  }
  
  //创建签名文件
  private void createSignFile() {
        ByteArrayOutputStream baos = null;
        FileOutputStream fos = null;
        String path = null;  
        File file = null;
        try {  
            path = Environment.getExternalStorageDirectory() + File.separator + System.currentTimeMillis() + ".jpg"; 
            file = new File(path);
            fos = new FileOutputStream(file);
            baos = new ByteArrayOutputStream();
            //如果设置成Bitmap.compress(CompressFormat.JPEG, 100, fos) 图片的背景都是黑色的
            mSignBitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);  
            byte[] b = baos.toByteArray();  
            if (b != null) {  
                fos.write(b); 
            }  
        } catch (IOException e) {  
            e.printStackTrace();  
        } finally {  
            try {  
                if (fos != null) {
                  fos.close();
                }
                if (baos != null) {
                  baos.close();
                }
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
  }
}

PaintView.java

package com.jackie.handwriting;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
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.view.MotionEvent;
import android.view.View;

public class PaintView extends View {
  private Paint mPaint;
  private Path mPath;
  private Bitmap mBitmap;
  private Canvas mCanvas;

  private int screenWidth, screenHeight;
  private float currentX, currentY;

  public PaintView(Context context, int screenWidth, int screenHeight) {
    super(context);
    this.screenWidth = screenWidth;
    this.screenHeight = screenHeight;
    init();
  }

  private void init() {
    mPaint = new Paint();
    mPaint.setAntiAlias(true); // 去除锯齿
    mPaint.setStrokeWidth(5);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setColor(Color.BLACK);

    mPath = new Path();

    mBitmap = Bitmap.createBitmap(screenWidth, screenHeight, Config.ARGB_8888);
    mCanvas = new Canvas(mBitmap);
//    mCanvas.drawColor(Color.WHITE);
  }

  @Override
  protected void onDraw(Canvas canvas) {
    canvas.drawBitmap(mBitmap, 0, 0, null);
    canvas.drawPath(mPath, mPaint);
  }

  @Override
  public boolean onTouchEvent(MotionEvent event) {
    float x = event.getX();
    float y = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
      currentX = x;
      currentY = y;
      mPath.moveTo(currentX, currentY);
      break;
    case MotionEvent.ACTION_MOVE:
      currentX = x;
      currentY = y;
      mPath.quadTo(currentX, currentY, x, y); // 画线
      break;
    case MotionEvent.ACTION_UP:
      mCanvas.drawPath(mPath, mPaint);
      break;
    }

    invalidate();
    return true;
  }

  public Bitmap getPaintBitmap() {
    return resizeImage(mBitmap, 320, 480);
  }
  
  public Path getPath() {
    return mPath;
  }

  // 缩放
  public static Bitmap resizeImage(Bitmap bitmap, int width, int height) {
    int originWidth = bitmap.getWidth();
    int originHeight = bitmap.getHeight();

    float scaleWidth = ((float) width) / originWidth;
    float scaleHeight = ((float) height) / originHeight;

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

  //清除画板
  public void clear() {
    if (mCanvas != null) {
      mPath.reset();
      mCanvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
            invalidate();
    }
  }
}

WritePadDialog.java

package com.jackie.handwriting;

import android.app.Dialog;
import android.content.Context;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.Toast;

public class WritePadDialog extends Dialog {
  private Context mContext;
  private WriteDialogListener mWriteDialogListener;
  private PaintView mPaintView;
  private FrameLayout mFrameLayout;
  private Button mBtnOK, mBtnClear, mBtnCancel;

  public WritePadDialog(Context context,
      WriteDialogListener writeDialogListener) {
    super(context);
    this.mContext = context;
    this.mWriteDialogListener = writeDialogListener;
  }

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE); //无标题
    setContentView(R.layout.write_pad);

    mFrameLayout = (FrameLayout) findViewById(R.id.tablet_view);

    // 获取屏幕尺寸
    DisplayMetrics mDisplayMetrics = new DisplayMetrics();
    getWindow().getWindowManager().getDefaultDisplay().getMetrics(mDisplayMetrics);
    int screenWidth = mDisplayMetrics.widthPixels;
    int screenHeight = mDisplayMetrics.heightPixels;
    mPaintView = new PaintView(mContext, screenWidth, screenHeight);
    mFrameLayout.addView(mPaintView);
    mPaintView.requestFocus();

    mBtnOK = (Button) findViewById(R.id.write_pad_ok);
    mBtnOK.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {
        if (mPaintView.getPath().isEmpty()) {
          Toast.makeText(mContext, "请写下你的大名", Toast.LENGTH_SHORT).show();
          return;
        }
        mWriteDialogListener.onPaintDone(mPaintView.getPaintBitmap());
        dismiss();
      }
    });

    mBtnClear = (Button) findViewById(R.id.write_pad_clear);
    mBtnClear.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {
        mPaintView.clear();
      }
    });

    mBtnCancel = (Button) findViewById(R.id.write_pad_cancel);
    mBtnCancel.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {
        cancel();
      }
    });
  }
}

WriteDilogListener.java

package com.jackie.handwriting;

/**
 * 监听手写板对话框
 * @author chengcj1
 * 
 */
public interface WriteDialogListener {
  public void onPaintDone(Object object);
}

效果如下：