Question

在我的MainActivity我有一个方法showPopUp，由按钮的监听器调用。所以MainActivity's布局只包含一个按钮。

ShowPopUp方法读取按钮状态并返回null pointer expception。 activity_toggle是包含toggleButton的布局。以下是我的主要活动代码段。

public class MainActivity extends ActionBarActivity {
  ToggleButton toggleButton;
  String i;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    showAlertDialog(MainActivity.this);
}

public void showAlertDialog(final Context context){
AlertDialog.Builder ab = new AlertDialog.Builder(context);
View v = LayoutInflater.from(context).inflate(R.layout.activity_toggle,null);
ab.setView(v);
ab.setTitle("toggle mera dil toggle meri jaan");
   toggleButton = (ToggleButton)findViewById(R.id.toggleButton1);


toggleButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        if(toggleButton.isChecked()){
                i+=i;
                Toast.makeText(MainActivity.this,"Button is on "+i,Toast.LENGTH_SHORT).show();
            }
            else{
                Toast.makeText(MainActivity.this,"Button is off  mode",Toast.LENGTH_SHORT).show();
            }
    }
});
ab.setPositiveButton("Ok",new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
    Toast.makeText(MainActivity.this,"ok button pressed",Toast.LENGTH_SHORT).show();
    boolean tButton = toggleButton.isChecked();
    if(tButton){
        Toast.makeText(MainActivity.this,"Button is off on a ",Toast.LENGTH_SHORT).show();
    }

    dialog.dismiss();
}
});
ab.setNegativeButton("Cancel",new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        dialog.dismiss();
    }
});
ab.create().show();
}
}

Answer 1

尝试以下代码。当你从inflater视图中找到视图时，你必须提供View的参考。

toggleButton =（ToggleButton）v.findViewById（R.id.toggleButton1）;

View v = LayoutInflater.from(context).inflate(R.layout.activity_toggle,null);
ab.setView(v);
ab.setTitle("toggle mera dil toggle meri jaan");
toggleButton = (ToggleButton)v.findViewById(R.id.toggleButton1);

Answer 2

使用v查看从setView传递AlertDialog方法的对象，以便从对话框布局访问ToggleButton：

 toggleButton = (ToggleButton)v.findViewById(R.id.toggleButton1);

Answer 3

toggleButton = (ToggleButton)findViewById(R.id.toggleButton1);

此行在您的活动中查找视图，但此R.id.toggleButton1控件在对话框中使用的activity_toggle.xml布局中定义。试试

toggleButton = (ToggleButton)v.findViewById(R.id.toggleButton1);

在alert对话框中使用layout（toggleButton），总是返回nullPointerExpection

3 个答案: