如何在phonegap中创建插件以在后台运行应用程序？

Question

我已经在phonegap中创建了后台服务插件（在后台运行应用程序）。

这是我的插件的java代码：

public class BackgroundService extends Plugin {
    @Override
    public PluginResult execute(String action, JSONArray args, String callbackId)
    {
        PluginResult.Status status = PluginResult.Status.OK;
        String result = "";

        try {
            if (action.equals("onCreate")) {
                this.onCreate();
            }
            else if (action.equals("onBind")) {
                Intent intent = null;
                this.onBind(intent);
            }
            else if (action.equals("onDestroy")) {
                this.onDestroy();
            }
            else if (action.equals("onStart")) {
                Intent intent = null;
                this.onStart(intent,args.getInt(1));
            }
            else if (action.equals("onUnbind")) {
                Intent intent = null;
                this.onUnbind(intent);
            }
            return new PluginResult(status, result);
        } catch(JSONException e) {
            return new PluginResult(PluginResult.Status.JSON_EXCEPTION);
        }
    }
    public void onCreate() {

        // TODO Auto-generated method stub



        }
    public IBinder onBind(Intent intent) {

        // TODO Auto-generated method stub



        return null;

        }
    public void onDestroy() {

        // TODO Auto-generated method stub

        super.onDestroy();



        }
    public void onStart(Intent intent, int startId) {

        // TODO Auto-generated method stub

        //super.onStart(intent, startId);



        }
    public boolean onUnbind(Intent intent) {

        // TODO Auto-generated method stub



        }
    public void onPause()
    {
        super.webView.loadUrl("javascript:navigator.BackgroundService.onBackground();");
    }

    public void onResume()
    {
        super.webView.loadUrl("javascript:navigator.BackgroundService.onForeground();");
    }

}

我的js文件是：

function BackgroundService() {
};

BackgroundService.prototype.create = function() {
    PhoneGap.exec(null, null, "BackgroundService", "onCreate", []);
};

BackgroundService.prototype.destroy = function() {
    PhoneGap.exec(null, null, "BackgroundService", "onDestroy", []);
};

BackgroundService.prototype.start = function(intent,startId) {
    PhoneGap.exec(null, null, "BackgroundService", "onStart", [intent,startId]);
};

BackgroundService.prototype.bind = function(intent) {
    PhoneGap.exec(null, null, "BackgroundService", "onBind", [intent]);
};

BackgroundService.prototype.unbind = function(intent) {
    PhoneGap.exec(null, null, "BackgroundService", "onUnbind", [intent]);
};
PhoneGap.addConstructor(function() {
    PhoneGap.addPlugin("BackgroundService", new BackgroundService());
});

并在我的index.html中。我在按钮中添加了以下代码

navigator.BackgroundService.onCreate（）;  navigator.BackgroundService.onStart（意向，1）;

我的错误是：

ERROR/AndroidRuntime(14981): FATAL EXCEPTION: main

ERROR/AndroidRuntime(14981): java.lang.RuntimeException: Unable to instantiate service com.app.newly.BackgroundService: java.lang.ClassCastException: com.app.newly.BackgroundService

ERROR/AndroidRuntime(14981):at android.app.ActivityThread.handleCreateService(ActivityThread.java:2943)

ERROR/AndroidRuntime(14981):at android.app.ActivityThread.access$3300(ActivityThread.java:125)

ERROR/AndroidRuntime(14981):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2087)
ERROR/AndroidRuntime(14981):     at android.os.Handler.dispatchMessage(Handler.java:99)

ERROR/AndroidRuntime(14981):     at android.os.Looper.loop(Looper.java:123)

ERROR/AndroidRuntime(14981):     at android.app.ActivityThread.main(ActivityThread.java:4627)
ERROR/AndroidRuntime(14981):     at java.lang.reflect.Method.invokeNative(Native Method)

ERROR/AndroidRuntime(14981):     at java.lang.reflect.Method.invoke(Method.java:521)

ERROR/AndroidRuntime(14981):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)

ERROR/AndroidRuntime(14981):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
ERROR/AndroidRuntime(14981):     at dalvik.system.NativeStart.main(Native Method)
ERROR/AndroidRuntime(14981): Caused by: java.lang.ClassCastException: com.app.newly.BackgroundService
ERROR/AndroidRuntime(14981):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2940)
ERROR/AndroidRuntime(14981):     ... 10 more

如果我从java文件中删除 startService（new Intent（this，MyService.class））; ，我收到以下错误：

ERROR/Web Console(4785): ReferenceError: Can't find variable: SqlitePlugin at file:///android_asset/www/BackgroundService.js:31
ERROR/Web Console(4785): TypeError: Result of expression 'window.plugins.SqlitePlugin' [undefined] is not an object. at file:///android_asset/www/index.html:26

否则我无法运行应用程序我在java文件中收到错误。在此行的左下角获得红色十字标记（如“ X ”） startService（new Intent（this，MyService.class））;'请告诉我我哪里错了，请指导我，提前谢谢。

 我在启动服务中收到错误。当我将光标移动到startService时，我正在获取create方法'startService（intent）'

而且我对这个插件有疑问我能否在后台运行javascript。如果有可能如何在后台获取警报。请告诉我哪里错了，请指导我，谢谢你提前。

Answer 1

创建插件很好。您可以像普通的java文件一样创建服务。 然后，只要你调用这个插件。你就像

一样开始你的服务

startService(new Intent(this, MyService.class));

然后您的服务将在后台运行。这是一种简单的方法。

如果单独创建服务，则

您的插件应如下所示

public class BackgroundService extends Plugin {

private static final String TAG = "BackgroundService";
private static final String CALL_SERVICE_ACTION = "callService";

@Override
public PluginResult execute(String action, JSONArray args, String callbackId)
{
    Log.i(TAG, "Plugin Called");
PluginResult result = null;

if (CALL_SERVICE_ACTION.equals(action)) {
    Log.d(TAG, "CALL_SERVICE_ACTION");
    startService(new Intent(ctx, MyService.class));
}

else {
    result = new PluginResult(Status.INVALID_ACTION);
    Log.d(TAG, "Invalid action : " + action + " passed");
}

return result;
}
}

您的 .js 文件应如下所示

function BackgroundService() {
};

BackgroundService.prototype.callService = function(successCallback, failCallback) {

return PhoneGap.exec(successCallback, failCallback, "BackgroundService",
    "callService", [ null ]);
};

PhoneGap.addConstructor(function() {
PhoneGap.addPlugin("BackgroundService", new BackgroundService());
});

您的 HTML 文件应如下所示

function callServiceFunction() {
window.plugins.BackgroundService.callService('callService',
        callServiceSuccessCallBack, callServiceFailCallBack);

}
function callServiceSuccessCallBack(e) {
alert("Success");
}

function callServiceFailCallBack(f) {
alert("Failure");
}

您还需要在res / xml / plugins.xml中注册phonegap插件，如

<plugin name="BackgroundService" value="package-structure.BackgroundService"/>

Answer 2

在从DroidGap扩展的Java类的onCreate方法中，确保已正确设置“keepRunning”。

        super.setBooleanProperty("keepRunning", true);