android 画图

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.trackdrawer03.MainActivity" >
<!--以上改了linearlayout的orientation-->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >

<Button
android:id="@+id/clrbtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="clear" />

<Button
android:id="@+id/savebtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="save" />
</LinearLayout>

<ImageView
android:id="@+id/iv_canvvas"
android:layout_width="match_parent"
android:layout_height="match_parent" />

</LinearLayout>

package com.example.trackdrawer03;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends Activity {

private Button clrbtn;
private ImageView ivcanvas;

private Canvas canvas;
private Paint paint;
private Bitmap baseBitmap;

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

clrbtn = (Button) findViewById(R.id.clrbtn);
ivcanvas = (ImageView) findViewById(R.id.iv_canvvas);

paint = new Paint();
paint.setColor(Color.RED);
paint.setStrokeWidth(3);

clronClickListner clrListner = new clronClickListner();

clrbtn.setOnClickListener(clrListner);
ivcanvas.setOnTouchListener(touch);

}

private View.OnTouchListener touch = new OnTouchListener() {

// 定义手指开始触摸的坐标
float startX;
float startY;

@Override
public boolean onTouch(View v, MotionEvent event) {
// TODO Auto-generated method stub

switch (event.getAction()) {

// 用户按下动作
case MotionEvent.ACTION_DOWN:

// 第一次绘画初始化内存图片，指定背景为白色
if (baseBitmap == null) {
baseBitmap = Bitmap.createBitmap(ivcanvas.getWidth(),
ivcanvas.getHeight(), Bitmap.Config.ARGB_8888);
canvas = new Canvas(baseBitmap);
canvas.drawColor(Color.WHITE);
}
// 记录开始接触的点的坐标
startX = event.getX();
startY = event.getY();
break;
// 当用户手指在屏幕上移动的动作
case MotionEvent.ACTION_MOVE:
float stopX = event.getX();
float stopY = event.getY();

// 绘制
canvas.drawLine(startX, startY, stopX, stopY, paint);

// 更新
startX = event.getX();
startY = event.getY();

// 把图片展示到imageView中
ivcanvas.setImageBitmap(baseBitmap);
break;

case MotionEvent.ACTION_UP:
break;
default:
break;
}

return true;
}
};

//clear canvas

public void clearCanvas(){

if(baseBitmap!=null){
baseBitmap = Bitmap.createBitmap(ivcanvas.getWidth(),
ivcanvas.getHeight(),Bitmap.Config.ARGB_8888);
canvas = new Canvas(baseBitmap);
canvas.drawColor(Color.WHITE);
ivcanvas.setImageBitmap(baseBitmap);
Toast.makeText(getApplicationContext(), "clear successfully", 3000).show();

}

}

public class clronClickListner implements OnClickListener{

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
clearCanvas();
}

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}