oncreate 函数中的布局宽度为 0

Question

oncreate函数中的布局宽度，我需要这个大小，但你的勇气是0。这是我的一些代码：

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main); 
    LinearLayout layout_principal=(LinearLayout)findViewById(R.id.pru);
    int mywidth=layout_principal.getWidth();
    LinearLayout.LayoutParams txt_sep_principal_Params=new LinearLayout.LayoutParams(
            LinearLayout.LayoutParams.MATCH_PARENT,
            mywidth/2);
         TextView txt_sep_principal=new TextView(this);
         txt_sep_principal.setLayoutParams(txt_sep_principal_Params);
         txt_sep_principal.setText("text of my code");
         TextView txt_sep_principal2=new TextView(this);
         txt_sep_principal2.setLayoutParams(txt_sep_principal_Params);
         txt_sep_principal2.setText("Text of my code");
    layout_principal.addView(txt_sep_principal);
    layout_principal.addView(txt_sep_principal2);

}

Answer 1

在此行之后

 LinearLayout layout_principal=(LinearLayout)findViewById(R.id.pru);

尝试添加这些代码行。

layout_principal.setOrientation(LinearLayout.VERTICAL);
layout_principal.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));

Answer 2

现在在oncreate方法中获取布局的大小还为时过早

试试这个代码：

@Override
 public void onWindowFocusChanged(boolean hasFocus) {
 // TODO Auto-generated method stub
 super.onWindowFocusChanged(hasFocus);
 //Here you can get the size!
   Toast.makeText(this,""+ Layout.getHeight(), Toast.LENGTH_LONG).show();
}

在此处查看完整代码：

LinearLayout layout_principal;
    int mywidth;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main); 
        layout_principal =(LinearLayout)findViewById(R.id.pru);

        LinearLayout.LayoutParams txt_sep_principal_Params=new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT,
                mywidth/2);
             TextView txt_sep_principal=new TextView(this);
             txt_sep_principal.setLayoutParams(txt_sep_principal_Params);
             txt_sep_principal.setText("text of my code");
             TextView txt_sep_principal2=new TextView(this);
             txt_sep_principal2.setLayoutParams(txt_sep_principal_Params);
             txt_sep_principal2.setText("Text of my code");
        layout_principal.addView(txt_sep_principal);
        layout_principal.addView(txt_sep_principal2);
        }

     @Override
     public void onWindowFocusChanged(boolean hasFocus) {
     // TODO Auto-generated method stub
       super.onWindowFocusChanged(hasFocus);
      //Here you can get the size!
       mywidth=layout_principal.getWidth();
      }

Answer 3

layout可能尚未完全完成绘制。尝试在其上发布runnable。类似的东西

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main); 
    LinearLayout layout_principal=(LinearLayout)findViewById(R.id.pru);
    layout_principal.post(new Runnable()
    {       
      public void run()
      {
       int mywidth=layout_principal.getWidth();
       LinearLayout.LayoutParams txt_sep_principal_Params=new LinearLayout.LayoutParams(
       LinearLayout.LayoutParams.MATCH_PARENT,
       mywidth/2);
       TextView txt_sep_principal=new TextView(this);
       ...
    }
 });

编辑

public class YourActivty extends Activity
{
     // These are declarations
     TextView tv;
     Button btn;
     protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // these are initializations
        tv = (TextView) findViewById(R.id.someId);
        btn = (Button) findViewById(R.id.someOtherId);

请参阅我的代码中的注释。以这种方式声明它们使它们可供整个Activity使用。在调用setContentView()之前，您不能初始化它们，当然也不能在方法外部初始化它们。显然，您需要将我使用的示例View替换为您自己的示例。