Android 不同類別傳Activity

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Still being relatively new to this I'm having issues in finding a view in a non-activity class MyLocation which I'm using in my activity class MainActivity. I'm using MyLocation to get longitude and latitude. I want to highlight a textview when either GPS or Network has been used. To do so I need to find the textviews in the non-activity class MyLocation. Here is how I'm calling it in MainActivity: public class MainActivity extends ActionBarActivity implements LocationListener { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); MyLocation myLocation = new MyLocation(); myLocation.getLocation(this, locationResult); } And here what I tried in MyLocation to find the textviews: public class MyLocation { LocationManager lm; LocationResult locationResult; private Context context; TextView tvnetwork, tvgps; private int defaultTextColor; LocationListener locationListenerNetwork = new LocationListener() { public void onLocationChanged(Location location) { locationResult.gotLocation(location); LayoutInflater inflater = (LayoutInflater) context .getSystemService(Context.LAYOUT_INFLATER_SERVICE); View v = inflater.inflate(R.layout.main, null); tvnetwork = (TextView) v.findViewById(R.id.tvnetwork); tvgps = (TextView) v.findViewById(R.id.tvgps); defaultTextColor = tvgps.getTextColors().getDefaultColor(); tvnetwork.setTextColor(context.getResources().getColor( R.color.green)); tvgps.setTextColor(defaultTextColor); lm.removeUpdates(this); lm.removeUpdates(locationListenerGps); } public void onProviderDisabled(String provider) { } public void onProviderEnabled(String provider) { } public void onStatusChanged(String provider, int status, Bundle extras) { } }; But the views are not found. I already get a NPE @ .getSystemService(Context.LAYOUT_INFLATER_SERVICE);. What am I doing wrong? android layout-inflater shareimprove this question asked Sep 12 '14 at 11:25 sascha 80210

Where you have defined your getLocation method ? – Spring Breaker Sep 12 '14 at 11:27  very simple...when you are calling MyLocation class..just add context as parameter to it and thus you can get all the things from there on. – GvSharma Sep 12 '14 at 11:32 add a comment

3 Answers

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get a NPE @ .getSystemService(Context.LAYOUT_INFLATER_SERVICE);. What am I doing wrong? Because context is null in MyLocation class. use MyLocation class constructor to pass MainActivity context in MyLocation to access system services as: Activity activity; public MyLocation(Context context,Activity activity){ this.context=context; this.activity=activity; } and in MainActivity create MyLocation class object by passing MainActivity context as: MyLocation myLocation = new MyLocation(MainActivity.this,this); Now use context to access system services in MyLocation class EDIT: Instead of inflating main layout again in onLocationChanged use Activity context to access view from Activity Layout as: public void onLocationChanged(Location location) { .... tvnetwork = (TextView) activity.findViewById(R.id.tvnetwork); tvgps = (TextView) activity.findViewById(R.id.tvgps); defaultTextColor = tvgps.getTextColors().getDefaultColor(); tvnetwork.setTextColor(context.getResources().getColor( R.color.green)); tvgps.setTextColor(defaultTextColor); .... }

Android 多個view寫法

void initOnClickListener() {

        int my_ids[] = {
                R.id.button01, R.id.button02, R.id.button03, ...
        };

        Button b = null;
        for( int i=0 ; i< ids.length ; ++i )
                if( ( b = (Button)findViewById( my_ids[i]) ) != null )
                        b.setOnClickListener(this);
}

public void onClick(View v) {
        switch( v.getId() ) {
                case R.id.button01:
                        break;
                case R.id.button02:
                        break;
                // ...
        }
}

C# 用Linq+匿名物件寫法 直接組JSON

出處

用Linq+匿名物件寫法 直接組JSON

這招在Json.net的官方文件有範例(用JObject.FromObject的那個)：http://james.newtonking.com/projects/json/help/html/CreatingLINQtoJSON.htm

但只有範例，沒寫為什麼Linq要那樣寫，誰看得懂阿XD

要用Linq直接組JSON

大概把握幾點：

Json Object：Json字串用大括號{}表示，Linq也是用大括號{}表示

Json Object的Name(Key、Property)：Json字串在兩個雙引號””裡寫一個英文單字，Linq就直接寫英文單字即可

Json Array：Json字串用中括號[]表示，Linq就用from o in XXX select o，這種回傳IEnumerable的寫法(如果JSON字串是物件陣列的話就用from o in XXX select new {欄位1=YYY}這種形式)

Json Value：Linq就看Json字串填什麼值就跟著填什麼值

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)//Get Method
        {
            //準備資料
            List<string> registration_ids = new List<string>() { "4", "8", "15", "16", "23", "42" };

            //用Linq直接組
            var result = new
                            {
                                collapse_key = "score_update",
                                time_to_live = 108,
                                delay_while_idle = true,
                                data = new{
                                    score ="4x8",
                                    time = "15:16.2342"
                                },
                                registration_ids = from s in registration_ids
                                                            select s

                            };

            //序列化為JSON字串並輸出結果
            Response.Write(JsonConvert.SerializeObject(result));
        }
    }

Android map fragment 顯示按鈕

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/map"
    android:name="com.google.android.gms.maps.SupportMapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.LocationChooser">


    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right|top"
        android:text="Demo Button" 
        android:padding="10dp"
        android:layout_marginTop="20dp"
        android:paddingRight="10dp"/>

</fragment>