1. 如何显示与不显示ActionBar ?
如果Activity class 继承的是 Activity ， 无法显示ActionBar 。
已知的必定显示ActionBar的就是 ActionBarActivity
代码：
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.cool_menu,menu);
return true;
}
1.1 全屏加无状态栏：
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
2. OnTouch 方法中，如果return值设为false，系统检测到这个Touch动作做完反应后，就不会再检查这个状态；如果设为true，就会时时检查，于是可以实现拖动的效果。
3. 灰色的小提示框 Toast
Toast toast = Toast.makeText(this,"不知阁下尊姓大名？",Toast.LENGTH_LONG);
toast.setGravity(Gravity.CENTER,0,0);//设置显示的位置
toast.show();
4. findViewById() 用于查找和关联控件（button，TextView，ImageView 等）
5. 如果要查找Preference中的控件（如，CheckBoxPreference，EditTextPreference等）用以下方法：
PreferenceManager manager = getPreferenceManager();
CheckBoxPreference password = (EditTextPreference) manager.findPreference("password");
6. 获取Preference中的值使用：
PreferenceManager.getDefaultSharedPreferences(context).getString("user","");
或者分两步，方便查询同一个Preference中的多个值
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
boolean willMusic = sharedPreferences.getBoolean("music",true);
String username = sharedPreferences. getString("user","");
7. 给Intent带上附加值Ertra
Intent i = new Intent(CSM_listView.this,ImageViewer.class);
i.putExtra("icon",data.icon);
startActivity(i);
接收方可以接收查看附加数据
int icon = getIntent().getIntExtra("icon",0);
也可以分两步，方便查询多个附加数据
Bundle bundle = getIntent().getExtras();
boolean willContinue = bundle.getBoolean("continueGame",false);
int icon = bundle.getInt ("icon",0);
8. 发Intent启动Activity并获取返回值
i = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(Intent intent, int requestCode);
并定义对返回值的处理函数
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(resultCode == RESULT_OK ){ //操作没错误
Bundle extras = data.getExtras();
bmp = (Bitmap)extras.get("data");//关键词是“data”
viewPhoto.setImageBitmap(bmp);
}
}
9. 播放音乐
MediaPlayer mp;
mp = MediaPlayer.create(this,R.drawable.fengyanghuagu);
mp.setLooping(true);//循环播放
mp.setVolume(0.3f,0.3f);//设置音量
mp.start();
停止播放并释放占用的资源
mp.stop();
mp.release();
10. 对话提示框
10.1 带列表的提示框，点击列表项目启动对应的事件
new AlertDialog.Builder(this).setTitle(R.string.new_game_title)
.setItems(R.array.difficulty, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialoginterface, int i) { //i is the position of item clicked
startGame(i);
}
}).show();
注释：
/**
public void onClick(DialogInterface dialog, int which);
* This method will be invoked when a button in the dialog is clicked.
*
* @param dialog The dialog that received the click.
* @param which The button that was clicked (e.g.
* {@link DialogInterface#BUTTON1}) or the position
* of the item clicked.
*/
/* TODO: Change to use BUTTON_POSITIVE after API council */
10.2 带文本提示和按钮的提示框，点击按钮选择发生的事件
new AlertDialog.Builder(happyNewYear.this).setMessage("想继续游戏吗？").setPositiveButton("继续",new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Intent i = new Intent(happyNewYear.this,sudugame.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
i.putExtra("continueGame",true);
startActivity(i);
finish();
}
}).setNegativeButton("回主菜单",new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Intent i = new Intent(happyNewYear.this,sudugame.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
i.putExtra("continueGame",false);
startActivity(i);
finish();
}
}).show();
10.3 收起Dialog 的 函数
dismiss();
11. 防止手机进入休眠状态
PowerManager.WakeLock wl;
wl = pM.newWakeLock(PowerManager.FULL_WAKE_LOCK,"whatever");
wl.acquire();//启动休眠锁
wl.release();//释放休眠锁
更多模式参照 http://blog.csdn.net/airk000/article/details/9121003
12. 把较小的数据记录到Preference里方便下次继续，如游戏进度
getPreferences(MODE_PRIVATE).edit().putString(PREF_PUZZLE, toPuzzleString(puzzle)).putString("nochange_record",toPuzzleString(nochange_record)).commit();
//这里存放了两种记录数据，使用syntax sugar哎呦不错
调用存放的数据
puz = getPreferences(MODE_PRIVATE).getString(PREF_PUZZLE, easyPuzzle[0]);
tempNochange = getPreferences(MODE_PRIVATE).getString("nochange_record",emptyStr);
13. 关于StringBuilder
StringBuilder buf = new StringBuilder(); //使用StringBuilder制作string（由于要不停地在结尾添加字符，用这个更方便效率更高）
for(int element: puz){
buf.append(element);
}
return buf.toString();
14. 短时音效的使用（如枪声，按键音）
public SoundPool(int maxStreams, int streamType, int srcQuality)
* Constructor. Constructs a SoundPool object with the following
* characteristics:
*
* @param maxStreams the maximum number of simultaneous streams for this
* SoundPool object
* @param streamType the audio stream type as described in AudioManager
* For example, game applications will normally use
* {@link AudioManager#STREAM_MUSIC}.
* @param srcQuality the sample-rate converter quality. Currently has no
* effect. Use 0 for the default.
* @return a SoundPool object, or null if creation failed
* @deprecated use {@link SoundPool.Builder} instead to create and configure a
* SoundPool instance
*/
public int load(Context context, int resId, int priority)
* @param context the application context
* @param resId the resource ID
* @param priority the priority of the sound. Currently has no effect. Use
* a value of 1 for future compatibility.
* @return a sound ID. This value can be used to play or unload the sound.
*/
例子：
SoundPool sp;
int explosion = 0;
sp = new SoundPool(5, AudioManager.STREAM_MUSIC,0);
explosion = sp.load(game, R.raw.mie,1);
sp.setVolume(explosion,1,1);
sp.play(explosion,1,1,0,0,1);//播放
15. 定义Paint的字体
Paint foreground = new Paint(Paint.ANTI_ALIAS_FLAG);//反锯齿画笔
foreground.setStyle(Style.FILL); //充满
foreground.setTextSize(height * 0.75f); //字体大小
foreground.setTextScaleX(width / height); //字体高宽比
foreground.setTextAlign(Paint.Align.CENTER);// 字体居格子中间
FontMetrics fm = foreground.getFontMetrics();// Centering in X: use alignment (and X at midpoint)
float x = width / 2;// Centering in Y: measure ascent/descent first
float y = height / 2 - (fm.ascent + fm.descent) / 2;
16. 清除之前的Activity 的stack 记录，使返回键无法返回（用于游戏结束收尾）
Intent i = new Intent(sudu_success.this,happyNewYear.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
finish();
17. 画图
canvas.drawBitmap(happyNY,changeX,changeY,null);
18. 延时
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
19. 多线程
Thread sleeper = new Thread(){
public void run(){
try {
sleep(1200);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
sleeper.start();
try {
sleeper.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
20. 做混合应用的时候webview 添加JavascriptInterface 后 js掉用方法 出现undefined 调试了一下午终于找到原因：
在绑定的方法前一定要加
@JavascriptInterface
否则在某些手机(比如红米)的webview中会出现调用方法时undefined的情况