public class Toast {   public static final int LENGTH_SHORT = 0;   public static final int LENGTH_LONG = 1;     /**   * 構(gòu)造一個空的toast。你必須在調(diào)動show()之前，線調(diào)用setView()   * @param context 參數(shù)，application或者activity都可以   */  public Toast(Context context) {   ...   //獲取系統(tǒng)內(nèi)置的toast_y_offset常量值   mTN.mY = context.getResources().getDimensionPixelSize(     com.android.internal.R.dimen.toast_y_offset);   mTN.mGravity = context.getResources().getInteger(     com.android.internal.R.integer.config_toastDefaultGravity);  }   /**   * 在指定的時長顯示view視圖   */  public void show() {   //如果mNextView為空，即沒有設置view   if (mNextView == null) {    throw new RuntimeException("setView must have been called");   }    //通過系統(tǒng)服務，獲取通知管理器。看來這是使用系統(tǒng)通知？   INotificationManager service = getService();   String pkg = mContext.getOpPackageName();   TN tn = mTN;   tn.mNextView = mNextView;    try {    service.enqueueToast(pkg, tn, mDuration);   } catch (RemoteException e) {    // Empty   }  }    /**   * 關閉一個正在顯示的toast, 或者取消一個未顯示的toast.   * 通常你不必調(diào)用它，在適當?shù)臅r長后它會自動消失的。   */  public void cancel() {   mTN.hide();    try {    getService().cancelToast(mContext.getPackageName(), mTN);   } catch (RemoteException e) {    // Empty   }  }   /**   * 設置toast顯示的視圖內(nèi)容，不單單是黑色的界面，你可以自己決定顯示什么   * @see #getView   */  public void setView(View view) {   mNextView = view;  }   /**   * 設置時長，只能是下面這兩個常量值，沒什么卵用   * @see #LENGTH_SHORT 2000毫秒   * @see #LENGTH_LONG 3500毫秒   */  public void setDuration(@Duration int duration) {   mDuration = duration;  }    /**   * 設置view的外間距，不用多說.   *   * @param horizontalMargin The horizontal margin, in percentage of the   *  container width, between the container's edges and the   *  notification   * @param verticalMargin The vertical margin, in percentage of the   *  container height, between the container's edges and the   *  notification   */  public void setMargin(float horizontalMargin, float verticalMargin) {   mTN.mHorizontalMargin = horizontalMargin;   mTN.mVerticalMargin = verticalMargin;  }    /**   * 設置notification在屏幕中的方位，大家都知道.上中下左中右什么的都有   * @see android.view.Gravity   * @see #getGravity   */  public void setGravity(int gravity, int xOffset, int yOffset) {   mTN.mGravity = gravity;   mTN.mX = xOffset;   mTN.mY = yOffset;  }     /**   * 構(gòu)造一個只包含一個TextView的標準toast對象   *   * @param context 通常是application或者activity對象   * @param text  用于顯示的文本，可以是formatted text.   * @param duration 顯示時長. LENGTH_SHORT或LENGTH_LONG   *   */  public static Toast makeText(Context context, CharSequence text, @Duration int duration) {   Toast result = new Toast(context);    LayoutInflater inflate = (LayoutInflater)     context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);    //包含了一個默認的TextView，這個textview的布局位置在  com.android.internal.R.layout.transient_notification，可以去查看下內(nèi)容   View v = inflate.inflate(com.android.internal.R.layout.transient_notification, null);   TextView tv = (TextView)v.findViewById(com.android.internal.R.id.message);   tv.setText(text);      result.mNextView = v;   result.mDuration = duration;    return result;  }     /**   * 更新通過makeText()方法創(chuàng)建出來的toast對象顯示的文本內(nèi)容   * @param s 待顯示的新文本內(nèi)容.   */  public void setText(CharSequence s) {   if (mNextView == null) {    throw new RuntimeException("This Toast was not created with Toast.makeText()");   }    /**    * 看來com.android.internal.R.layout.transient_notification布局里面的唯一的    * TextView標簽的id是R.id.message。拿到這個textview，設置新文本內(nèi)容    */   TextView tv = (TextView) mNextView.findViewById(com.android.internal.R.id.message);   if (tv == null) {    throw new RuntimeException("This Toast was not created with Toast.makeText()");   }   tv.setText(s);  }    static private INotificationManager getService() {   if (sService != null) {    return sService;   }   //獲取遠程的通知服務   sService = INotificationManager.Stub.asInterface(ServiceManager.getService("notification"));   return sService;  }    //TN是一個瞬態(tài)通知的子類，里面包含顯示和隱藏兩個任務對象  private static class TN extends ITransientNotification.Stub {   final Runnable mShow = new Runnable() {    @Override    public void run() {     handleShow();    }   };    final Runnable mHide = new Runnable() {    @Override    public void run() {     handleHide();     // Don't do this in handleHide() because it is also invoked by handleShow()     mNextView = null;    }   };     //出現(xiàn)Handler了哦   final Handler mHandler = new Handler();     /**    * 調(diào)度handleShow任務到執(zhí)行線程中    */   @Override   public void show() {    if (localLOGV) Log.v(TAG, "SHOW: " + this);    //handler發(fā)送異步任務了    mHandler.post(mShow);   }     /**    * 同上    */   @Override   public void hide() {    if (localLOGV) Log.v(TAG, "HIDE: " + this);    mHandler.post(mHide);   }    //...  }  } 

Toast.makeText(context, text, duration).show(); 

Toast toast = Toast.makeText(context, text, duration); pre name="code" class="html"> toast.setView(view); toast.setText(s); toast.setGravity(gravity, xOffset, yOffset); toast.setDuration(duration); toast.show();

Toast toast = new Toast(); toast.setView(view); toast.setText(s); toast.setGravity(gravity, xOffset, yOffset); toast.setDuration(duration); toast.show(); 

public class T {  private static Toast toast;   public static void show(Context context, String msg) {   if (toast == null) {    toast = Toast.makeText(context, msg, Toast.LENGTH_SHORT);   } else {    toast.setText(msg);   }   toast.show();  } }