更改主活动中按钮的背景

Question

我已经创建了一个类，它扩展了对话片段。在该类中，当我按下一个按钮时，我想更改一个按钮的背景，该按钮被放置在主活动中。

我试图创建一个内部类来访问Main Active对象，但我得到的是这个错误：

尝试在空对象引用上调用虚拟方法android.content.pm.Application ationInfoandroid.content.Context.getApplication ationInfo（）

@SuppressLint("ValidFragment")
public class Popup extends DialogFragment {
    private final MediaPlayer _mediaPlayer = new MediaPlayer();
    private final int _layout;
    private TextInputEditText _customTextField;
    private final Dialog mDialog = new Dialog();
    public boolean dialogIsActive = false;

    @SuppressLint("ValidFragment")
    public Popup(int layout) {
        _layout = layout;
    }

    public interface ICustomTts {
        void customTts(String input, Activity activity);
    }
    public ICustomTts iCustomTts;

    public interface  ITarget {
        String getTarget(String input);
    }
    public ITarget iTarget;

    @SuppressLint({"ClickableViewAccessibility", "ResourceType"})
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        final View view =  inflater.inflate(_layout, container, false);

        // Display fragment_dialog
        if (_layout == R.layout.fragment_dialog) {
            // Read and display the expressions
            view.findViewById(R.id.dialogHelp).setOnClickListener(v -> {
                String expressions = null;
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    expressions = Helper.readFile(getContext(), "expressions.yml");
                }
                TextView models = view.findViewById(R.id.dialogModels);
                models.setText(expressions);
            });
            // Toggle the listener
            Button cta = view.findViewById(R.id.dialogCta);

            // Gain access to MainActivity
            class InnerMainActivity extends my.app.MainActivity {
                @RequiresApi(api = Build.VERSION_CODES.M)
                public void dialog(boolean active) {
                    int button = (active) ? R.drawable.button_red : R.drawable.button_yellow;
                    findViewById(R.id.dialog).setBackground(ContextCompat.getDrawable(getContext(), button));
                }
            }
            InnerMainActivity innerMainActivity = new InnerMainActivity();

            cta.setOnClickListener(v -> {
                if (!dialogIsActive) {
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                        if (mDialog.hasRecordPermission(getContext())) {
                            mDialog.startService(getContext());
                            cta.setBackground(ContextCompat.getDrawable(getContext(), R.drawable.button_red));
                            cta.setText(R.string.dialog_do_not_listen);
                            cta.setTextSize(17);
                            innerMainActivity.dialog(true);
                            dialogIsActive = true;
                        }
                    }
                }
                else {
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                        mDialog.stopTheService(getContext());
                        cta.setBackground(ContextCompat.getDrawable(getContext(), R.drawable.button_yellow));
                        cta.setText(R.string.dialog_listen);
                        innerMainActivity.dialog(false);
                        dialogIsActive = false;
                    }
                }
            });
        }
                
        return view;
    }      

}

Answer 1

你可以使用接口做到这一点。在你的对话片段：

public class MyDialog extends DialogFragment {

public interface OnButtonClick {
    void onButtonClick(boolean active);
}

private OnButtonClick onButtonClick;

public MyDialog(OnButtonClick onButtonClick) {
    this.onButtonClick = onButtonClick;
}
...

在你的活动中

MyDialog myDialog= new MyDialog(new MyDialog.OnButtonClick(){
        @Override
        public void onButtonClick(boolean active) {
            // TODO change background
        }
    });