無法以編程方式創建按鈕陣列而沒有錯誤

Question

該代碼塊對我無效。我調試了，我認爲錯誤來自setlayoutparams，但它沒有任何意義，因爲如果我取出for循環並創建一個按鈕（而不是一個按鈕數組），那麼它會工作。

Button btn[] = new Button[oNumber]; 
    for (int i=0;i<oNumber;i++){ 
     btn[i].setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT)); 
     btn[i].setText(oName[i]); 
     System.out.println("making b's"); 
     layout.addView(btn[i]); 
    } 

這是我得到的錯誤。我確實有清單中正確寫入的活動。

08-14 12:45:56.482: E/AndroidRuntime(4060): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.rcontrol/com.example.rcontrol.ViewTarget}: java.lang.NullPointerException 

Answer 1

您創建的按鈕的排列，但並沒有將其初始化：更多詳細

Button btn[] = new Button[oNumber]; 
for (int i=0;i<oNumber;i++){ 
    btn[i] = new Button(this); // initialize it 
    btn[i].setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT)); 
    btn[i].setText(oName[i]); 
    System.out.println("making b's"); 
    layout.addView(btn[i]); 
} 

Answer 2

。

int oNumber = 4;

String oName[] = {"x","2","3","4"}; 
    Button btn[] = new Button[oNumber]; 
    LinearLayout layout = (LinearLayout) findViewById(R.id.layout1); 

    for (int i=0;i<oNumber;i++){ 
     btn[i] = new Button(this); // initialize it 
     btn[i].setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT)); 
     btn[i].setText(oName[i]); 
     btn[i].setOnClickListener(this); 
     System.out.println("making b's"); 
     layout.addView(btn[i]); 
    }