Android调试- 删除TextView,Button和Layout引发崩溃

Question

当我点击按钮来删除一个TextView ，Button 和 LinearLayout.时，程序崩溃。下面是logcat输出，当我想在118行删除View时就崩溃了。

  tasklayout.removeView(taskbutton);

04-15 14:35:58.222: E/AndroidRuntime(632): java.lang.NullPointerException
04-15 14:35:58.222: E/AndroidRuntime(632):  at com.com.com.addtask.deltask(addtask.java:118)
04-15 14:35:58.222: E/AndroidRuntime(632):  at com.com.com.addtask$2.onClick(addtask.java:65)
04-15 14:35:58.222: E/AndroidRuntime(632):  at android.view.View.performClick(View.java:3511)
04-15 14:35:58.222: E/AndroidRuntime(632):  at android.view.View$PerformClick.run(View.java:14105)
04-15 14:35:58.222: E/AndroidRuntime(632):  at android.os.Handler.handleCallback(Handler.java:605)

onClickListner 和 deltask void

Button delt = (Button) findViewById(R.id.btndelete1);
    delt.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {
            deltask(v);
        }
    });
public void deltask(View v) {

    SharedPreferences datatask;
    datatask = getSharedPreferences(filename, 0);
    int tnum = datatask.getInt("tasknumber", 1);
    int layoutnum = 1000 + tnum;
    int textviewnum = 1100 + tnum;
    int buttonviewnum = 1200 + tnum;

    LinearLayout layout = (LinearLayout) findViewById(R.id.taskll);
    LinearLayout tasklayout = (LinearLayout) findViewById(layoutnum);
    TextView tasktv = (TextView) findViewById(textviewnum);
    Button taskbutton = (Button) findViewById(buttonviewnum);

    tasklayout.removeView(taskbutton);
    tasklayout.removeView(tasktv);
    layout.removeView(tasklayout);
}

Answer 1

估计是tasklayout为空，而tasklayout的赋值语句似乎有问题：
LinearLayout tasklayout = (LinearLayout) findViewById(layoutnum);
这个layoutnum似乎是你计算出来的一个数字，不是一个正确的资源ID，找不到对应的Layout View，tasklayout为null，就会导致tasklayout.removeView(xx)报空指针错。