我是Android Graphics类的新手。我想使用触摸事件绘制图像(实际上是签名类型),并希望在我想保存时将其保存在SD卡上。我已经通过网络扫描了任何这样的教程,但我还没有找到。谁能告诉我如何使用触摸事件在画布上绘制并保存它。
任何教程或示例代码都会有很大帮助。
答案 0 :(得分:21)
我在android开发人员身上看到了非常好的代码,但我再也找不到它了......它的输出是bezier曲线,所以它会非常流畅。这是我编辑的代码:
public class MyDrawView extends View {
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
private Paint mPaint;
public MyDrawView(Context c) {
super(c);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(0xFF000000);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(3);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
canvas.drawPath(mPath, mPaint);
}
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private void touch_start(float x, float y) {
mPath.reset();
mPath.moveTo(x, y);
mX = x;
mY = y;
}
private void touch_move(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
mX = x;
mY = y;
}
}
private void touch_up() {
mPath.lineTo(mX, mY);
// commit the path to our offscreen
mCanvas.drawPath(mPath, mPaint);
// kill this so we don't double draw
mPath.reset();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}
public void clear(){
mBitmap.eraseColor(Color.TRANSPARENT);
invalidate();
System.gc();
}}
然后在onCreate of activity中你想用它来写下这样的东西:
RelativeLayout parent = (RelativeLayout) findViewById(R.id.signImageParent);
myDrawView = new MyDrawView(this);
parent.addView(myDrawView);
此视图是透明的,并使用黑色绘画用手指绘制。因此,如果你想看到你画的东西,只需在这个视图的背景上绘制一个白色或灰色的位图(你只需在onDraw的beginnig中添加一行),或者你可以使用父级的背景。
然后,当您想要根据绘制的图像创建图像时,只需调用
即可parent.setDrawingCacheEnabled(true);
Bitmap b = parent.getDrawingCache();
FileOutputStream fos = null;
try {
fos = new FileOutputStream(getFileName());
} catch (FileNotFoundException e) {
e.printStackTrace();
}
b.compress(CompressFormat.PNG, 95, fos);
这取决于您想要输出的内容,您可以使用此代码或代替 parent ,您可以使用 myDrawView 执行此操作,您只需获得图像即可没有背景绘制(因为我们的myDrawView背景透明)。
希望这会有所帮助。随意留下反馈。
答案 1 :(得分:20)
绘图事物
Scribbler.java:
package org.yourpackage.scribble;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
public class Scribbler extends Activity {
DrawView drawView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
drawView = new DrawView(this);
drawView.setBackgroundColor(Color.WHITE);
setContentView(drawView);
drawView.requestFocus();
}
}
DrawView.java:
package org.yourpackage.scribble;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
public class DrawView extends View implements OnTouchListener {
List<Point> points = new ArrayList<Point>();
Paint paint = new Paint();
public DrawView(Context context) {
super(context);
setFocusable(true);
setFocusableInTouchMode(true);
this.setOnTouchListener(this);
paint.setColor(Color.BLACK);
}
@Override
public void onDraw(Canvas canvas) {
for (Point point : points) {
canvas.drawCircle(point.x, point.y, 2, paint);
}
}
public boolean onTouch(View view, MotionEvent event) {
Point point = new Point();
point.x = event.getX();
point.y = event.getY();
points.add(point);
invalidate();
return true;
}
}
class Point {
float x, y;
}
的AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="org.yourpackage.scribble"
android:versionCode="1"
android:versionName="1.0">
<application>
<activity android:name=".Scribbler">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-sdk android:minSdkVersion="3" />
</manifest>
..会给你这样的东西:
您可能想要绘制线条而不是像素
保存的东西
要实施保存,您可以将Bitmap
传递到Canvas
构造函数,然后使用compress
Bitmap
创建可以写入SD卡的OutputStream
的方法
编辑回答你的评论:
当然,您可以使用XML来定义布局,因为DrawView
扩展了View,您可以在布局xml文件中使用它。
main.xml
布局文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:id="@+id/linearLayout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/gradient"
>
<Button android:text="Button" android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
<org.yourpackage.scribble.DrawView android:id="@+id/drawView1" android:layout_width="wrap_content" android:layout_height="wrap_content"> </at.gru.android.drawdemo.DrawView>
</LinearLayout>
给你这样的东西:
您只需要一个额外的contstructor public DrawView(Context context, AttributeSet attrSet)