Android的toast.makeText方面的错误 [英] Android toast.makeText context error

问题描述

我无法调用toast.Maketext位置监听器内。上下文是不可用，我究竟做错了什么？

 私人LocationListener的LL =新LocationListener的（）{    公共无效onLocationChanged（位置L）{
        // SMSReceiver.l = 1;
        字符串s =;
        S + =\\ 970 12：+ l.getTime（）+\\ n;
        S + =\\ tLatitude：+ l.getLatitude（）+°\\ N的;
        S + =\\ tLongitude：+ l.getLongitude（）+°\\ N的;
        S + =\\ tAccuracy：+ l.getAccuracy（）+米\\ N的;
        S + =\\ tAltitude：+ l.getAltitude（）+米\\ N的;
        S + =\\ tSpeed​​：+ l.getSpeed​​（）+米\\ N的;        // TODO自动生成方法存根
        如果（l.hasSpeed​​（））{
            myspeed的= l.getSpeed​​（）;
        }        Log.i（DEBUG_TAG，在当前位置更改：（+ S +））;
ERROR这里 - ＆GT; Toast.makeText（上下文，S，Toast.LENGTH_SHORT）.show（）;
    }    公共无效onProviderDisabled（字符串为arg0）{
        // TODO自动生成方法存根    }    公共无效onProviderEnabled（字符串为arg0）{
        // TODO自动生成方法存根    }    公共无效onStatusChanged（字符串为arg0，ARG1 INT，捆绑ARG2）{
        // TODO自动生成方法存根    }};
 

解决方案

如果这个 LocationListener的的声明是一个活动类中（例如： MyActivity ），你应该创建吐司为：

  Toast.makeText（MyActivity.this，S，Toast.LENGTH_SHORT）.show（）;
 

在情况下， LocationListener的在无环境类被声明，就像在你的情况下，广播接收器，你可以通过上下文给它的构造：

 私人最后一类MyReceiver扩展广播接收器
{
    私人MyLocationListener侦听器;
    公共MyReceiver（最终上下文的背景下）
    {
        this.listener =新MyLocationListener（背景）;
    }    私人final类MyLocationListener实现LocationListener的
    {
        私人上下文的背景下;
        公共MyLocationListener（最终上下文的背景下）
        {
            this.context =背景;
        }        @覆盖
        公共无效onLocationChanged（地点）
        {
            // ...
            Toast.makeText（背景下，这里面包消息，Toast.LENGTH_SHORT）.show（）;
        }        //实现的方法，其余
    }    @覆盖
    公共无效的onReceive（上下文的背景下，意图意图）
    {
        //请注意，您在这里有一个背景下，您可以收到广播消息时使用
    }
}
 

I am having trouble calling toast.Maketext inside of a location listener. The context is not available, what am I doing wrong?

private LocationListener ll = new LocationListener() {

    public void onLocationChanged(Location l) {
        // SMSReceiver.l = l;
        String s = "";
        s += "\tTime: " + l.getTime() + "\n";
        s += "\tLatitude:  " + l.getLatitude() + "°\n";
        s += "\tLongitude: " + l.getLongitude() + "°\n";
        s += "\tAccuracy:  " + l.getAccuracy() + " metres\n";
        s += "\tAltitude:  " + l.getAltitude() + " metres\n";
        s += "\tSpeed:  " + l.getSpeed() + " metres\n";

        // TODO Auto-generated method stub
        if (l.hasSpeed()) {
            mySpeed = l.getSpeed();
        }

        Log.i(DEBUG_TAG, "On Location Changed: (" + s + ")");
ERROR HERE-->       Toast.makeText(context, s, Toast.LENGTH_SHORT).show();
    }

    public void onProviderDisabled(String arg0) {
        // TODO Auto-generated method stub

    }

    public void onProviderEnabled(String arg0) {
        // TODO Auto-generated method stub

    }

    public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
        // TODO Auto-generated method stub

    }

};

解决方案

If this LocationListener declaration is inside an activity class (say: MyActivity), you should create the Toast as:

Toast.makeText(MyActivity.this, s, Toast.LENGTH_SHORT).show();

In case the LocationListener is declared in a contextless class, like in your case a BroadcastReceiver, you can pass the context to its constructor:

private final class MyReceiver extends BroadcastReceiver
{
    private MyLocationListener listener; 
    public MyReceiver(final Context context)
    {
        this.listener = new MyLocationListener(context);
    }

    private final class MyLocationListener implements LocationListener
    {
        private Context context;
        public MyLocationListener(final Context context)
        {
            this.context = context; 
        }

        @Override
        public void onLocationChanged(Location location)
        {
            // ...
            Toast.makeText(context, "Toast message here", Toast.LENGTH_SHORT).show();
        }

        // implement the rest of the methods
    }

    @Override
    public void onReceive(Context context, Intent intent)
    {
        // Note that you have a context here, which you can use when receiving an broadcast message
    }
}

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