Android）如何使用系统后退按钮？

Question

我正在尝试为在我的程序中启动的浏览器提供返回功能。

我的平板电脑没有底栏

所以我是这样实现的。

import android.app.Activity;
import android.app.ActivityManager;
import android.app.Instrumentation;
import android.app.PendingIntent;
import android.app.Service;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.content.pm.PackageManager;
import android.graphics.PixelFormat;
import android.os.Build;
import android.os.IBinder;
import android.util.Log;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.RelativeLayout;
import android.widget.Toast;

import java.util.List;

import kr.co.green_.ConfirmDialog;
import kr.co.green_.ExampleAccessService;
import kr.co.green_.R;

import static android.content.ContentValues.TAG;

public class CloseBtnServiceForGallery extends Service {

    private WindowManager manager;
    private RelativeLayout parentlayout;
    private View mViewClose;
    private ImageButton btnClose;
    private ImageButton btnBack;
    private ExampleAccessService exService;

    @Override
    public IBinder onBind(Intent paramIntent) {
        return null;
    }
    @Override
    public void onCreate() {
        super.onCreate();
        Log.d(TAG, "CloseBtnServiceForGallery");
        LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
        this.mViewClose = inflater.inflate(R.layout.close_btn_gallery, null);
        this.exService = new ExampleAccessService();
        this.exService.onServiceConnected();

        btnClose = (ImageButton)this.mViewClose.findViewById(R.id.btnCloseGallery);
        btnBack = (ImageButton)this.mViewClose.findViewById(R.id.btnBack);
        btnClose.setOnClickListener(mCloseBtnClickListener);
        btnBack.setOnClickListener(mCloseBtnClickListener);

        this.manager = (WindowManager) getSystemService(WINDOW_SERVICE);
        WindowManager.LayoutParams params = null;

        if(Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
            params = new WindowManager.LayoutParams(
                    WindowManager.LayoutParams.WRAP_CONTENT,
                    WindowManager.LayoutParams.WRAP_CONTENT,
                    WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
                    WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                    PixelFormat.TRANSLUCENT);
        } else {
            params = new WindowManager.LayoutParams(
                    WindowManager.LayoutParams.WRAP_CONTENT,
                    WindowManager.LayoutParams.WRAP_CONTENT,
                    WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY,
                    WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                    PixelFormat.TRANSLUCENT);
        }

        params.gravity = Gravity.LEFT | Gravity.BOTTOM ;
        params.verticalMargin = 0.1f ;
        this.manager.addView(mViewClose, params);
    }


    Button.OnClickListener mCloseBtnClickListener = new Button.OnClickListener() {
        public void onClick(View v) {
            try{
                Log.e("try close", "v? : " + v);
                switch (v.getId()) {
                    case R.id.btnCloseGallery:
                        // something
                        break;
                    case R.id.btnBack:
                        try{
                            //exService.onServiceConnected(); This accessibility function requires system privileges so it can't be used

                            ActivityManager activity_manager = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);
                            List<ActivityManager.RunningTaskInfo> task_info = activity_manager.getRunningTasks(9999);
                            ComponentName componentInfo = task_info.get(0).topActivity;
                            ActivityInfo activityInfo = tryGetActivity(componentInfo);

                            // What should I do?
                            // I want to tell the current topmost activity to go back when a button click is detected in my plotted icon service.
                        }
                        catch(Exception e){
                            Log.e("error", ":" + e);
                        }
                        break;

                    default:
                        break;
                }
            }catch(Exception e){
                Log.e("try close click","error :"  + e);
            }
      
        }
    };

    private ActivityInfo tryGetActivity(ComponentName componentName) {
        try {
            return getPackageManager().getActivityInfo(componentName, 0);
        } catch (PackageManager.NameNotFoundException e) {
            return null;
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        if (this.manager != null) {
            if (this.mViewClose != null) {
                this.manager.removeView(this.mViewClose);
                this.mViewClose = null;
            }
            this.manager = null;
        }
    }
}

下图使用 Instrumentation，但也需要系统权限。
mycode

mycode2

我的程序在后台运行 在顶部屏幕上浮动图标。
myapp

但是这种方法需要系统权限。

我想在没有系统权限的情况下将其实现为应用程序

This is the app I want

谢谢

Answer 1

//声明值 私有布尔返回 = false;

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            if (Back) {
                setResult(RESULT_OK);
                finish();
            } else {
                setResult(RESULT_CANCELED);
                finish();
            }

        }
        return super.onKeyDown(keyCode, event);
    }

    
------------------ OR ------------------

@Override
public void onBackPressed() {
    super.onBackPressed();
    finish();
    startActivity(new Intent(SecActivity.this, FirstActivity.class));
}