Avoid Call Instance Method in Constructor to Prevent NullPointerException

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• Related Posts
• Avoid Call Instance Method in Constructor

• How to Avoid NullPointerException in Java Part 1
• How to Avoid NullPointerException in Java Part 2
• Avoid Call Instance Method in Constructor to Prevent NullPointerException

Avoid Call Instance Method in Constructor

Calling am instance method while the object is being constructed is anti-pattern and error prone, can easily lead to bugs.

public class MyDialog extends Dialog {

  private final TextView bodyText;

  public MyDialog(Context context) {
    super(context);
    setContentView(R.layout.dialog);
    bodyText = findViewById(R.id.text);
  }

  public void setText( CharSequence text) {
    bodyText.setText(text);
  }

  public CharSequence getProgressBarText() {
    return bodyText.getText();
  }
}

Checker framework would report error like below:

error: [method.invocation.invalid] call to setContentView(int) not allowed on the given receiver.
    setContentView(R.layout.dialog);
                  ^
  found   : @UnderInitialization(android.app.Dialog.class) @NonNull Dialog
  required: @Initialized @NonNull Dialog
MyDialog.java error: [method.invocation.invalid] call to <T>findViewById(int) not allowed on the given receiver.
    bodyText = findViewById(R.idtext);
                           ^
  found   : @UnderInitialization(android.app.Dialog.class) @NonNull Dialog
  required: @Initialized @NonNull Dialog

This can be fixed:

public class MyDialog extends Dialog {

  public static MyDialog newInstance(Context context) {
    View dialogView = LayoutInflater.from(context).inflate(R.layout.dialog, null);
    MyDialog dialog = new MyDialog(context, dialogView);
    dialog.setUp(dialogView);
    return dialog;
  }

  private final TextView bodyText;

  private CarProgressDialog(Context context, View dialogView) {
    super(context);
    bodyText = Preconditions.checkNotNull(dialogView.findViewById(R.id.text));
  }

  public void setProgressBarText(CharSequence text) {
    bodyText.setText(text);
  }

  public CharSequence getProgressBarText() {
    return bodyText.getText();
  }
}

Another approach:

public class MyDialog extends Dialog {

  private CharSequence text;
  @MonotonicNonNull private TextView bodyText;

  public MyDialog(Context context) {
    super(context);
    this.text = "";
  }
  public MyDialog(Context context, CharSequence text) {
    super(context);
    this.text = text;
  }

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.dialog);

    bodyText = findViewById(R.id.text);
    bodyText.setText(text);
  }

  public void setText(CharSequence text) {
    this.text = text;
    if (bodyText != null) {
      bodyText.setText(text);
    }
  }

  public CharSequence getText() {
    return text;
  }
}