Android Launcher 学习

今天学习下 写一个 非常非常简陋的 launcher ,下面内容：

一、大概内容
1.该过程中使用 GridView 存放每一个 app
2.每个 app 包括 图标和 app名称，点击后 打开该 app
3.因此该过程中使用到 自定义 的 layout 和 adapter
4.其中主要的是获取 app 信息

二、MainActivity 内容

public class MainActivity extends AppCompatActivity {

    private GridView gridView = null;
    private String TAG = "MainActivity";
    private List mApps = null;
    private AppsAdapter appsAdapter = null;
    private WindowManager wm = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

       gridView = (GridView)findViewById(R.id.apps_list);
     //获取 app 信息，信息放在 list中
        Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
        mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);
        mApps = getPackageManager().queryIntentActivities(mainIntent, 0);

     //得到 手机屏幕的大小，在改代码中 没有使用
        wm = this.getWindowManager();
        DisplayMetrics dm = new DisplayMetrics();
        wm.getDefaultDisplay().getMetrics(dm);

        int width = (int) (dm.widthPixels / dm.density);
        int height =(int) (dm.heightPixels / dm.density);

        Log.e(TAG,"width: " + String.valueOf(width) + "hight: " + String.valueOf(height));

        //自定义的 adapter
        appsAdapter = new AppsAdapter(mApps,this,R.layout.cust_gridview);
        gridView.setAdapter(appsAdapter);
        //设置 每个app的点击事件
        gridView.setOnItemClickListener(listener);

    }

    private AdapterView.OnItemClickListener listener = new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView parent, View view, int position, long id) {
            ResolveInfo info = mApps.get(position);
            //得到app的包名 和 名称
            String pkg = info.activityInfo.packageName;
            String cls = info.activityInfo.name;

            ComponentName componet = new ComponentName(pkg, cls);
          //启动app
            Intent i = new Intent();
            i.setComponent(componet);
            startActivity(i);
        }
    };
}

三、 adapter 的内容

public class AppsAdapter extends BaseAdapter{

    private List mApps = null;
    private Context context = null;
    private int resourceId = 0;

    public AppsAdapter(List mApps,Context context,int resourceId) {
        this.mApps = mApps;
        this.context = context;
        this.resourceId = resourceId;
    }

    @Override
    public int getCount() {
        return mApps.size();
    }

    @Override
    public Object getItem(int position) {
        return mApps.get(position);
    }

    @Override
    public long getItemId(int position) {
       return  position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View v = LayoutInflater.from(context).inflate(resourceId,parent,false);
        ImageView i = (ImageView)v.findViewById(R.id.image);
        TextView textView = (TextView)v.findViewById(R.id.text);
        ResolveInfo info = mApps.get(position);
        //设置 APP image  和 名称
        i.setImageDrawable(info.activityInfo.loadIcon(context.getPackageManager()));

textView.setText(context.getPackageManager().getApplicationLabel(info.activityInfo.applicationInfo));

        return v;
    }
}

四、对应的 自定义 布局

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

LinearLayout>

五、activity_main 内容

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <GridView
        android:id="@+id/apps_list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:numColumns="4"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp">
    GridView>
LinearLayout>

六、设置全屏 styles.xml

    -- Base application theme. -->
    

七、作为 launcher 必须要设置的

 <category android:name="android.intent.category.HOME" />
 <category android:name="android.intent.category.DEFAULT" />

八、参考
1.https://blog.csdn.net/a1510624979/article/details/53115298
2.https://www.jb51.net/article/38823.htm
3.https://blog.csdn.net/flyyhz/article/details/78475602
4.https://www.cnblogs.com/playing/archive/2011/04/13/2014705.html

以上为学习的内容