android 提示框

1.在测试时,如何实现一个提示

可以使用

Toast.makeText(this, "这是一个提示", Toast.LENGTH_SHORT).show();
//从资源文件string.xml 里面取提示信息
Toast.makeText(this, getString(R.string.welcome), Toast.LENGTH_SHORT).show();

这个提示会几秒钟后消失

2.可以使用AlertDialog.Builder 才产生一个提示框.

   例如像messagebox那样的

   new AlertDialog.Builder(this)
     .setTitle("Android 提示")
     .setMessage("这是一个提示,请确定")
     .show();

带一个确定的对话框

new AlertDialog.Builder(this)
          .setMessage("这是第二个提示")
          .setPositiveButton("确定",
                         new DialogInterface.OnClickListener(){
                                 public void onClick(DialogInterface dialoginterface, int i){
                                     //按钮事件
                                  }
                          })
          .show();

AlertDialog.Builder 还有很多复杂的用法,有确定和取消的对话框

new AlertDialog.Builder(this)
         .setTitle("提示")
         .setMessage("确定退出?")
         .setIcon(R.drawable.quit)
         .setPositiveButton("确定", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int whichButton) {
         setResult(RESULT_OK);//确定按钮事件
         finish();
         }
         })
         .setNegativeButton("取消", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int whichButton) {
         //取消按钮事件
         }
         })
         .show();

3.menu 的用法.

public static final int ITEM_1_ID = Menu.FIRST;
public static final int ITEM_2_ID = Menu.FIRST + 1;
public static final int ITEM_3_ID = Menu.FIRST + 2;
    
public boolean onCreateOptionsMenu(Menu menu) {
         super.onCreateOptionsMenu(menu);
//不带图标的menu
         menu.add(0, ITEM_1_ID, 0, "item-1");       
//带图标的menu
         menu.add(0, ITEM_2_ID, 1, "item-2").setIcon(R.drawable.editbills2);
         menu.add(0, ITEM_3_ID, 2, "item-3").setIcon(R.drawable.billsum1);
        return true;
}

public boolean onOptionsItemSelected(MenuItem item){
       switch (item.getItemId()) {
       case 1:
            Toast.makeText(this, "menu1",Toast.LENGTH_SHORT).show();            
           return true;
       case 2:
        
           return true;
       case 3:
         
           return true;
        }
       return false;
     }

4.Activity 的切换

     2个Activity 的切换,没有数据传递

//从A到B
Intent intent = new Intent();
                 intent.setClass(A.this, B.class);
                 startActivity(intent);

2个Activity 之间传递数据

    相关的几个函数
     startActivityForResult
    public final void setResult(int resultCode, String data)
    回调函数

    protected void onActivityResult(int requestCode, int resultCode, Intent data)

    例如A到B,从B得到数据 

//A到B
static final int RG_REQUEST = 0;
Intent intent = new Intent();
intent.setClass(A.this, B.class);
startActivityForResult(intent,RG_REQUEST);
                                  
//在B中处理
Bundle bundle = new Bundle();
bundle.putString("DataKey", edittext.getText().toString());//给bundle 写入数据
Intent mIntent = new Intent();
mIntent.putExtras(bundle);
setResult(RESULT_OK, mIntent);
finish();

//最后在A的回调函数里面接收数据
if (requestCode == RG_REQUEST) {
     if (resultCode == RESULT_CANCELED)
           setTitle("Canceled...");
     else if(resultCode == RESULT_OK) {
          setTitle((String)data.getCharSequenceExtra("DataKey"));
        }
}