Android一些小技巧

1:设置选中图片的背景颜色 
this.gridviewToolbar = (GridView) super.findViewById(R.id.gridviewbar); 
this.gridviewToolbar.setSelector(new ColorDrawable(Color.TRANSPARENT)); 

2:通过屏幕的长度，宽度来定义控件的长宽 
this.width = super.getWindowManager().getDefaultDisplay().getWidth() 
/ this.menu_img.length; 
this.height = super.getWindowManager().getDefaultDisplay().getHeight() / 8; 

3:退出的对话框 
private void exitDialog() { 
Dialog dialog = new AlertDialog.Builder(this) 
.setMessage("您确定要退出本程序吗？") 
.setPositiveButton("确定", new DialogInterface.OnClickListener() { 

@Override 
public void onClick(DialogInterface dialog, int which) { 
LoginActivity.this.finish() ; 
} 
}) 
.setNegativeButton("取消", new DialogInterface.OnClickListener() { 

@Override 
public void onClick(DialogInterface dialog, int which) { 
} 
}).create(); 

dialog.show(); 
} 


@Override 
public boolean onKeyDown(int keyCode, KeyEvent event) { 
if(keyCode == KeyEvent.KEYCODE_BACK) { 
this.exitDialog() ; 
} 
return false ; 
} 
4:取消标题,必须在设置布局文件之前取消掉 
super.requestWindowFeature(Window.FEATURE_NO_TITLE);