Android -- queryIntentActivities

某些时候你想要知道某个APP是否有注册了一个明确的intent，比如说你想要检查某个receiver是否存在，然后根据是否存在来这个receiver来在你的AP里面enable某些功能。我们可以通过PackageManager来check它。

code

public boolean isIntentAvailable(Context context, String action) {
    final PackageManager packageManager = context.getPackageManager();
    final Intent intent = new Intent(action);
    List<ResolveInfo> resolveInfo = packageManager.queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);
   if (resolveInfo.size() > 0) {
        return true;
    }
   return false;
}

干货

一般APP的manifest里面要设置为launcher的activity总是要设置intent-filter：

<intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
</intent-filter>

可以通过queryIntentActivities来获得有哪些launcher：

private void loadApps() {
        Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
        mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);
        mApps = getPackageManager().queryIntentActivities(mainIntent, 0);
    }

我们可以在自己的app上用一个gridview显示出当前手机有哪些app：

import java.util.List;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.ResolveInfo;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
public class MyHome extends Activity
{
    GridView mGrid;             

    @Override
   public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        loadApps();
        setContentView(R.layout.main);
        mGrid = (GridView) findViewById(R.id.apps_list);
        mGrid.setAdapter(new AppsAdapter());
    }        

    private List<ResolveInfo> mApps;  

    private void loadApps() {
        Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
        mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);
        mApps = getPackageManager().queryIntentActivities(mainIntent, 0);
    }    

    public class AppsAdapter extends BaseAdapter
    {
        public AppsAdapter() {         }
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView i;
            if (convertView == null) {
                i = new ImageView(MyHome.this);
                i.setScaleType(ImageView.ScaleType.FIT_CENTER);
                i.setLayoutParams(new GridView.LayoutParams(50, 50));
            } else {
                i = (ImageView) convertView;
            }
            ResolveInfo info = mApps.get(position);
            i.setImageDrawable(info.activityInfo.loadIcon(getPackageManager()));
            return i;
        }
        public final int getCount() {
            return mApps.size();
        }
        public final Object getItem(int position) {
            return mApps.get(position);
        }
        public final long getItemId(int position) {
            return position;
        }
    }
}

可以设置点击监听器去开启app：

@Override 

public void onItemClick(AdapterView<?> parent, View view, int position,long id) {
    ResolveInfo info = mApps.get(position);
    //该应用的包名
    String pkg = info.activityInfo.packageName;
    //应用的主activity类
    String cls = info.activityInfo.name;
    ComponentName componet = new ComponentName(pkg, cls);
    Intent i = new Intent();
    i.setComponent(componet);
    startActivity(i);
}

我是天王盖地虎的分割线