Android中实现双缓冲（画板应用）和XML文件定义菜单

来源：互联网   发布日期：2016-01-14 12:23:09   浏览：3673次  

1.什么是双缓冲技术？双缓冲技术就是当用户操作界面完成后，会有一个缓冲区保存用户操作的结果。

为什么要使用双缓冲技术？拿Android 游戏开发来说，界面贞每次都是全部重画的，也就说画了新的，旧的就没了，所以需要使用双缓冲技术保存之前的内容。

如何实现双缓冲？使用一个Bitmap对象保留之前的画布即可。

package com.example.phonegaptest;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.content.Context;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.graphics.Bitmap;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.graphics.Bitmap.Config;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.graphics.Canvas;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.graphics.Color;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.graphics.Paint;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.graphics.Path;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.util.AttributeSet;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.view.MotionEvent;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.view.View;

public class DrawView extends View {

float preX;

float preY;

private Path path;

public Paint paint = null;

final int VIEW_WIDTH = 320;

final int VIEW_HEIGHT = 480;

Bitmap cacheBitmap = null;

Canvas cacheCanvas = null;

public DrawView(Context context, AttributeSet set) {

super(context, set);

cacheBitmap = Bitmap.createBitmap(VIEW_WIDTH, VIEW_HEIGHT,

Config.ARGB_8888);

cacheCanvas = new Canvas();

path = new Path();

cacheCanvas.setBitmap(cacheBitmap);

paint = new Paint(Paint.DITHER_FLAG);

paint.setColor(Color.RED);

paint.setStyle(Paint.Style.STROKE);

paint.setStrokeWidth(1);

paint.setAntiAlias(true);

paint.setDither(true);

}

@Override

public boolean onTouchEvent(MotionEvent event) {

float x = event.getX();

float y = event.getY();

switch (event.getAction()) {

case MotionEvent.ACTION_DOWN:

path.moveTo(x, y);

preX = x;

preY = y;

break;

case MotionEvent.ACTION_MOVE:

path.quadTo(preX, preY, x, y);

preX = x;

preY = y;

break;

case MotionEvent.ACTION_UP:

cacheCanvas.drawPath(path, paint);

path.reset();

break;

}

invalidate();

return true;

}

@Override

protected void onDraw(Canvas canvas) {

super.onDraw(canvas);

Paint bmpPaint = new Paint();

canvas.drawBitmap(cacheBitmap, 0, 0, bmpPaint);

canvas.drawPath(path, paint);

}

}

2.XMl文件实现菜单功能

XMl文件如下：

<?xml version="1.0" encoding="utf-8"?>

<menu xmlns:<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>="http://schemas.<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.com/apk/res/<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>" >

<item

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:id="@+id/close"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:icon="@drawable/ic_launcher"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:orderInCategory="3"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:title="Close"/>

<item

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:id="@+id/no_icon"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:orderInCategory="2"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:title="Sans Icon"/>

<item

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:id="@+id/disabled"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:enabled="true"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:orderInCategory="4"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:title="Disabled"/>

<!-- orderInCategory表示的是item的排序-->

<group

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:id="@+id/other_stuff"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:menuCategory="secondary"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:visible="true" >

<item

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:id="@+id/later"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:orderInCategory="0"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:title="2nd-To-Last"/>

<item

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:id="@+id/last"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:orderInCategory="1"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:title="Last"/>

</group>

<!--表示的是二级菜单-->

<item

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:id="@+id/submenu"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:orderInCategory="3"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:title="A Submenu">

<menu>

<item

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:id="@+id/non_ghost"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:alphabeticShortcut="n"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:title="Non-Ghost"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:visible="true"/>

<item

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:id="@+id/ghost"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:alphabeticShortcut="g"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:title="A Ghost"

<a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>:visible="true"/>

</menu>

</item>

</menu>

主文件

package com.example.receiveractivity;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.app.Activity;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.os.Bundle;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.util.Log;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.view.Menu;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.view.MenuInflater;

import <a title="android" href="http://www.android-study.com/pingtaikaifa/553.html">android</a>.view.MenuItem;

public class ReceiverActivity extends Activity {

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

private static final String TAG="BruceZhang";

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_receiver);

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// TODO Auto-generated method stub

MenuInflater mflater=new MenuInflater(this);

mflater.inflate(R.menu.activity_receiver, menu);

return super.onCreateOptionsMenu(menu);

}

@Override

public boolean onOptionsItemSelected(MenuItem item) {

// TODO Auto-generated method stub

switch(item.getItemId()){

case R.id.close:

Log.v(TAG, "------------close");

break;

case R.id.no_icon:

Log.v(TAG, "------------noicon");

break;

case R.id.submenu:

Log.v(TAG, "------------submenu");

break;

case R.id.non_ghost:

Log.v(TAG, "------------non_ghost");

break;

case R.id.ghost:

Log.v(TAG, "------------ghost");

break;

case R.id.disabled:

Log.v(TAG, "------------disabled");

break;

case R.id.last:

Log.v(TAG, "------------last");

break;

case R.id.later:

Log.v(TAG, "------------laster");

break;

default:

break;

}

return super.onOptionsItemSelected(item);

}

}

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