Android(安卓)setting中添加桌面循环滑动选项

首先，我前面有一片博客写的是android桌面（launch2）循环滑动，这里想加以改进，因为在我们所使用的手机中已经在“设置”的“辅助功能”中有选择是否“桌面循环”。

这里我想做的就是在原生的android源码上添加这一功能，主要还是以学习为主。

看这个之前我希望你们看一下android桌面（launch2）循环滑动这篇博客。

首先我是在做好了桌面循环之后去做在“设置”中添加这一项，所以怎么去做循环滑动这里就不再讲。

先看看图片吧：

这里的循环桌面就是我添加的。

先讲一下思路吧：先把界面做出来，再将是否选择的值存到系统的（adb shell进入）data/data/com.android.providers.settings/databases/settings.db数据库中的system表中，

然后在Launch2的源码中取得数据库中是否选择循环桌面来执行相关代码。

先做UI：

在settings源码中的accessibility_settings.xml文件中添加一个checkbox：

 <!-- add by xxnan -->    <CheckBoxPreference            android:key="launch_repeat"            android:title="@string/launch_repeat_title"            android:persistent="false"/>

在settings源码的res中添加相关的代码：

在values/string.xml中添加（英文显示）：

<string name="launch_repeat_title">Launch Repeat</string>

在values-zh-rCN/string.xml中添加（中文显示）：

在settings源码的AccessibilitySettings.java中的OnCreate中添加：

/*****************************************/        mLaunchRepeat=(CheckBoxPreference) findPreference(            LAUNCH_REPEAT); int LaunchRepeat=Settings.System.getInt(this.getContentResolver(),                    "launch_repeat",0);//取出是否被选择 if(LaunchRepeat==1)//如果被选择，那么下次打开setting时就勾选 mLaunchRepeat.setChecked(true); else mLaunchRepeat.setChecked(false);//如果没被选择，那么下次打开setting时就不勾选/*****************************************/

当然还要定义几个量：

private final String LAUNCH_REPEAT =
"launch_repeat";
private CheckBoxPreference mLaunchRepeat;

在onPreferenceTreeClick函数中添加：

//add by xxnan  if(LAUNCH_REPEAT.equals(key)) {                 Settings.System.putInt(getContentResolver(),                    "launch_repeat",                    ((CheckBoxPreference) preference).isChecked()? 1:0);//将是否选择存到系统的system表中       }         //add by xxnan

如果做好了之后当你点击选择“桌面循环时”可以到（adb shell进入）data/data/com.android.providers.settings/databases下的settings.db数据库（sqlite3 settings.db）的system

表中看到33|launch_repeat|1（select * from system；）。

到这里就完成了将数据存到系统system表中以及UI，接下来就是在Launch2源码中去取这个值（是否循环）。

到Launcher2源码中去找到Workspace.java文件，在里面有相应的修改：

在onTouchEvent中，之前我们有修改循环，如下：

 case MotionEvent.ACTION_UP:            if (mTouchState == TOUCH_STATE_SCROLLING) {                final VelocityTracker velocityTracker = mVelocityTracker;                velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);                final int velocityX = (int) velocityTracker.getXVelocity(mActivePointerId);                               final int screenWidth = getWidth();                final int whichScreen = (mScrollX + (screenWidth / 2)) / screenWidth;                final float scrolledPos = (float) mScrollX / screenWidth; Log.i("velocityX","velocityX="+velocityX+"whichScreen="+whichScreen);         /***********************************************/         //modifided by xxnan                      if (velocityX > SNAP_VELOCITY) {                    // Fling hard enough to move left.                    // Don't fling across more than one screen at a time.                    Log.i("numscreen","numscreen="+mCurrentScreen);                   /* final int bound = scrolledPos < whichScreen ?                           ( (mCurrentScreen+ getChildCount()) - 1 )% getChildCount(): mCurrentScreen;*/                     final int bound =( (mCurrentScreen+ getChildCount()) - 1 )% getChildCount() ; Log.i("numscreen","bound="+bound);                    snapToScreen( bound, velocityX, true);                } else if (velocityX < -SNAP_VELOCITY ) {                    // Fling hard enough to move right                    // Don't fling across more than one screen at a time.                    /*final int bound = scrolledPos > whichScreen ?                           ( mCurrentScreen + 1 )% getChildCount(): mCurrentScreen;*/                       final int bound = ( mCurrentScreen + 1 )% getChildCount() ;                         snapToScreen(bound, velocityX, true);                } else {                    snapToScreen(whichScreen, 0, true);                }         /***********************************************/                 //下面是原生代码                /*if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {                    // Fling hard enough to move left.                    // Don't fling across more than one screen at a time.                    final int bound = scrolledPos < whichScreen ?                            mCurrentScreen - 1 : mCurrentScreen;                    snapToScreen(Math.min(whichScreen, bound), velocityX, true);                } else if (velocityX < -SNAP_VELOCITY && mCurrentScreen < getChildCount() - 1) {                    // Fling hard enough to move right                    // Don't fling across more than one screen at a time.                    final int bound = scrolledPos > whichScreen ?                            mCurrentScreen + 1 : mCurrentScreen;                    snapToScreen(Math.max(whichScreen, bound), velocityX, true);                } else {                    snapToScreen(whichScreen, 0, true);                }*/            }            mTouchState = TOUCH_STATE_REST;            mActivePointerId = INVALID_POINTER;            releaseVelocityTracker();            break;

那么我们就要在修改的地方加一个判断，如果system中取得的值是1，就可以循环，如果是0，就不能。

代码修改如下：

 case MotionEvent.ACTION_UP:            if (mTouchState == TOUCH_STATE_SCROLLING) {                final VelocityTracker velocityTracker = mVelocityTracker;                velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);                final int velocityX = (int) velocityTracker.getXVelocity(mActivePointerId);                               final int screenWidth = getWidth();                final int whichScreen = (mScrollX + (screenWidth / 2)) / screenWidth;                final float scrolledPos = (float) mScrollX / screenWidth; Log.i("velocityX","velocityX="+velocityX+"whichScreen="+whichScreen);         /***********************************************/         //modifided by xxnan 2013-1-9             launch_repeat=Settings.System.getInt(mContext.getContentResolver(),                    "launch_repeat",0);//取出system表中“launch_repeat”的值 Log.i(" launch_repeat"," launch_repeat="+ launch_repeat);if(launch_repeat==1)//如果是1，就循环，也就是之前已经改好的{          if (velocityX > SNAP_VELOCITY) {                    // Fling hard enough to move left.                    // Don't fling across more than one screen at a time.                    Log.i("numscreen","numscreen="+mCurrentScreen);                   /* final int bound = scrolledPos < whichScreen ?                           ( (mCurrentScreen+ getChildCount()) - 1 )% getChildCount(): mCurrentScreen;*/                     final int bound =( (mCurrentScreen+ getChildCount()) - 1 )% getChildCount() ; Log.i("numscreen","bound="+bound);                    snapToScreen( bound, velocityX, true);                } else if (velocityX < -SNAP_VELOCITY ) {                    // Fling hard enough to move right                    // Don't fling across more than one screen at a time.                    /*final int bound = scrolledPos > whichScreen ?                           ( mCurrentScreen + 1 )% getChildCount(): mCurrentScreen;*/                       final int bound = ( mCurrentScreen + 1 )% getChildCount() ;                         snapToScreen(bound, velocityX, true);                } else {                    snapToScreen(whichScreen, 0, true);                }}else//如果是0，那么就是原生代码，不循环{                       if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {                    // Fling hard enough to move left.                    // Don't fling across more than one screen at a time.                    final int bound = scrolledPos < whichScreen ?                            mCurrentScreen - 1 : mCurrentScreen;                    snapToScreen(Math.min(whichScreen, bound), velocityX, true);                } else if (velocityX < -SNAP_VELOCITY && mCurrentScreen < getChildCount() - 1) {                    // Fling hard enough to move right                    // Don't fling across more than one screen at a time.                    final int bound = scrolledPos > whichScreen ?                            mCurrentScreen + 1 : mCurrentScreen;                    snapToScreen(Math.max(whichScreen, bound), velocityX, true);                } else {                    snapToScreen(whichScreen, 0, true);                }                       }         /***********************************************/                 //下面是原生代码                /*if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {                    // Fling hard enough to move left.                    // Don't fling across more than one screen at a time.                    final int bound = scrolledPos < whichScreen ?                            mCurrentScreen - 1 : mCurrentScreen;                    snapToScreen(Math.min(whichScreen, bound), velocityX, true);                } else if (velocityX < -SNAP_VELOCITY && mCurrentScreen < getChildCount() - 1) {                    // Fling hard enough to move right                    // Don't fling across more than one screen at a time.                    final int bound = scrolledPos > whichScreen ?                            mCurrentScreen + 1 : mCurrentScreen;                    snapToScreen(Math.max(whichScreen, bound), velocityX, true);                } else {                    snapToScreen(whichScreen, 0, true);                }*/            }            mTouchState = TOUCH_STATE_REST;            mActivePointerId = INVALID_POINTER;            releaseVelocityTracker();            break;

当然这里面也要定义几个量，以及导入几个包：

导入包：

//add by xxnan
import android.content.ContentResolver;//从system表中取数据
import android.provider.Settings;

定义变量：

private int launch_repeat;//取得是否循环的值

到这里就全部修改好了，还有就是编译一下源码中的package/apps的Launch2和Settings的源码，将生成的out/target/。。。/system/app下的

Launch2.apk和Settings.apk替换手机里system/app的这两个apk就可以了。

以下上本人亲手实现的，上面是实现的一些步骤，希望对大家有帮助！

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