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：