[移动开发]Qt拦截android back按键

一、直接在android中拦截

1.1 写一个java类MainActivity

package com.lsy.sharedata;

import java.util.Iterator;
import java.util.List;
import android.view.KeyEvent;
import android.Manifest;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Criteria;
import android.location.GpsSatellite;
import android.location.GpsStatus;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.location.LocationProvider;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.util.Log;

import android.widget.Toast;

public class MainActivity extends org.qtproject.qt5.android.bindings.QtActivity {

        private LocationManager lm;
        public static final String TAG="TAG";
        private static native void onExitApp(int exit);

        //设置权限用的
        private static final int BAIDU_READ_PHONE_STATE = 100;//定位权限请求
        private static final int PRIVATE_CODE = 1315;//开启GPS权限

        private static final String perms[] = {
                        Manifest.permission.ACCESS_FINE_LOCATION,
                        Manifest.permission.ACCESS_COARSE_LOCATION,
                        Manifest.permission.INTERNET
        };
        @Override
        public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);        
        } 
        @Override
        public boolean onKeyDown(int keyCode, KeyEvent event) {

                // 返回键移除二级悬浮窗
                if (keyCode == KeyEvent.KEYCODE_BACK
                                && event.getAction() == KeyEvent.ACTION_DOWN) {
                        Log.e(TAG, "back.....");
                        onExitApp(0);
                        //return true;
                }

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

1.2 在C++中注册回调：

void  QtCallAndroid::RegJni()
{
#ifdef Q_OS_ANDROID
    static JNINativeMethod methods[] {
        { "onGPSNotify", "(Ljava/lang/String;I)V", (void*)onGPSDataChanged },
        { "onExitApp", "(I)V", (void*)onAppExitChanged }
    };


    const char* kClassName ="com/lsy/sharedata/MainActivity";

    QtAndroid::runOnAndroidThreadSync([=](){

        QAndroidJniEnvironment qtEnv;
        jclass clazz;
        JNIEnv *EV = qtEnv.operator ->();

        clazz =EV->FindClass(kClassName);

        if (clazz == NULL)
        {
            qDebug()<<"erro   clazz";
            return ;
        }
        qDebug()<<"RegisterNatives   2***********";

        if (EV->RegisterNatives(clazz, methods, sizeof(methods) / sizeof(methods[0])) != JNI_OK)
        {
            printf("register native method failed!\n");
            return;
        }else{
            qDebug()<<"RegisterNatives   搞定***********";
        }

    });

    qDebug()<<"RegisterNatives   OK***********";
#endif
}

3.实现C++中回调函数：

void  QtCallAndroid::onAppExitChanged(JNIEnv *env, jobject thiz , jint exit)
{
    qDebug()<<"java send app exit..................";
}

?运行结果如下：

<!--Android中先拦截到Back按键-->
E TAG     : back.....
<!--注册到java中的回调次之-->
D libAcquireWealth_armeabi-v7a.so: DEBUG[ FILE: ..\..\AcquireWealth\qtcallandroid.cpp  LINE:97 ] java send app exit..................
<!-- Qt事件过滤器再次之-->
D libAcquireWealth_armeabi-v7a.so: DEBUG[ FILE: ..\..\AcquireWealth\qdoublecolorballmanager.cpp  LINE:854 ] back....................
<!-- 最后传回到QML-->
D libAcquireWealth_armeabi-v7a.so: qml: DEBUG[ FILE: qrc:/main.qml  LINE:92 ] accepted now
D libAcquireWealth_armeabi-v7a.so: qml: DEBUG[ FILE: qrc:/main.qml  LINE:93 ] 按下了返回按键.....

二、在Qt中拦截

2.1 写一个键盘事件过滤类 KeyPressFilter，主要重写eventFilter。

protected:
    //事件过滤
    bool eventFilter(QObject *watched, QEvent *event);

该函数具体实现：

bool KeyPressFilter::eventFilter(QObject *watched, QEvent *event)
{
    //获取事件类型
    if(event->type() == QEvent::KeyPress)
    {
        //转换成键盘事件
        QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
        //判断是否是back事件
        if(keyEvent->key() == Qt::Key_Back)
        {
            //发送back键按下的信号
            emit sigKeyBackPress();
            return true;
        }
    }
    return false;//
}

2.2 在main.cpp中把KeyPressFilter注册到qml并添加过滤器

    QQmlApplicationEngine engine;
    engine.rootContext()->setContextProperty("KeyPressFilter", KeyPressFilter::GetInstance());
    QQmlComponent component(&engine, QUrl("qrc:/main.qml"));
    //获取对象
    QObject *object = component.create();
    //添加过滤器
    KeyPressFilter::GetInstance()->SetFilter(object);

2.3 在main.qml中捕捉

        function onSigKeyBackPress(){

            console.log("按下了返回按键.....")
            
        }

效果如下图：