Android意向未启动活动

Question

After attempting to perform a search and failing, I am trying to launch an activity to display results from a search, but the app crashes when it gets to the point of the intent:

if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
    String query = intent.getStringExtra(SearchManager.QUERY);
    Intent mapIntent = new Intent(SearchActivity.this, MapResults.class);
    mapIntent.putExtra("query", query);
    startActivity(mapIntent);
}

here is the class it is supposed to launch:

public class MapResults extends MapActivity implements OnGestureListener, OnDoubleTapListener {
/** Called when the activity is first created. */

public String query;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    setContentView(R.layout.main);

        Intent intent = getIntent();
        query = intent.getStringExtra("query");

    Toast.makeText(this, "The query: " + query, Toast.LENGTH_LONG).show();
    }

    @Override
    public boolean isRouteDisplayed() {
        return false;
    }

and the manifest file:

<activity android:name=".SplashScreen"
    android:label="@string/app_name">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>
<activity android:name=".Main">
    <intent-filter>
        <action android:name="com.example.android.test.Main" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
    <meta-data android:name="android.app.default_searchable"
               android:value=".SearchActivity" />
</activity>
<activity android:name=".SearchActivity" 
    android:launchMode="singleTop" >
    <intent-filter>
        <action android:name="android.intent.action.SEARCH" />
    </intent-filter>
    <meta-data android:name="android.app.default_searchable"
        android:value=".SearchActivity" />
    <meta-data android:name="android.app.searchable"
        android:resource="@layout/searchable"/>
</activity>
<activity android:name=".MapResults">
    <intent-filter>
        <action android:name="com.example.android.test.MapResults"       
            android:label="@string/map_results_title"/>
    </intent-filter>
    <meta-data android:name="android.app.default_searchable"
        android:value=".SearchActivity" />
</activity>

I know that in the MapResults class it is not launching a map at the moment, its just displaying text, but this is just while I am trying to receive the data from the intent.

Any idea, cause I'm stuck!

Answer 1

<intent-filter>
    <action android:name="com.example.android.test.Main" />
    <category android:name="android.intent.category.DEFAULT" />
</intent-filter>

can you change DEFAULT to LAUNCHER? just try it

Answer 2

In your MapResults class, the line :

Toast.makeText(this, "The query: " + query, Toast.LENGTH_LONG).show();

will create a NullPointerException as you are concatenating a null String. Your data member query is null at this point, you should have something like this :

query = intent.getStringExtra( "query" );
Toast.makeText(this, "The query: " + query, Toast.LENGTH_LONG).show();

Otherwise, your mechanism to transfer data using intents seems alright to me.

Regards, Stéphane

Answer 3

The only problem, that I can see in the code is your intent variable is null, so it crashes on intent.getAction()

up: haven't noticed MapActivity code - if variable query is not initialized at the moment of Toast - yes, it's a second problem