多线性布局不工作

Question

两个LinearLayoutlinearfirstRow和linearsecondRow都有四个按钮each.First线性布局工作和第二个布局不显示。

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protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

     linearfirstRow=new LinearLayout(this); 
     linearfirstRow.setOrientation(LinearLayout.HORIZONTAL); 
     linearfirstRow.setId(1); 
     LinearLayout.LayoutParams Layoutparam1 = new LinearLayout.LayoutParams(
       LayoutParams.WRAP_CONTENT, 
       LayoutParams.WRAP_CONTENT,25);  
     linearfirstRow.setLayoutParams(Layoutparam1); 
     setContentView(linearfirstRow); 


     linearsecondRow=new LinearLayout(this); 
     linearsecondRow.setOrientation(LinearLayout.HORIZONTAL); 
     linearsecondRow.setId(2); 
     linearsecondRow.setLayoutParams(Layoutparam1); 


     btn_1=new Button(this); 
     btn_1.setLayoutParams(Layoutparam1); 
     btn_2=new Button(this); 
     btn_2.setLayoutParams(Layoutparam1); 
     btn_3=new Button(this); 
     btn_3.setLayoutParams(Layoutparam1); 
     btn_4=new Button(this); 
     btn_4.setLayoutParams(Layoutparam1); 

     btn_5=new Button(this); 
     btn_5.setLayoutParams(Layoutparam1); 
     btn_6=new Button(this); 
     btn_6.setLayoutParams(Layoutparam1); 
     btn_7=new Button(this); 
     btn_7.setLayoutParams(Layoutparam1); 
     btn_8=new Button(this); 
     btn_8.setLayoutParams(Layoutparam1); 

     linearfirstRow.addView(btn_1); 
     linearfirstRow.addView(btn_2); 
     linearfirstRow.addView(btn_3); 
     linearfirstRow.addView(btn_4); 

buttons are -->  linearsecondRow.addView(btn_5); 
notdisplayed  linearsecondRow.addView(btn_6); 
        linearsecondRow.addView(btn_7); 
        linearsecondRow.addView(btn_8); 

Answer 1

linearfirstrow是因为这个setContentView(linearfirstRow);

为linearsecondRow显示在onCreate()

addView(linearsecondRow);