Launcher里点击一个应用图标的内部流程分析

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从Android手机屏幕上点击一个应用图标进行启动Activity的过程分析如下：

/packages/apps/Launcher3/src/com/android/launcher3/Launcher.java

public class Launcher extends Activity

Launcher # startActivitySafely()

 @Thunk boolean startActivitySafely(View v, Intent intent, Object tag) {
        boolean success = false;
        if (mIsSafeModeEnabled && !Utilities.isSystemApp(this, intent)) {
            Toast.makeText(this, R.string.safemode_shortcut_error, Toast.LENGTH_SHORT).show();
            return false;
        }
            // ...关键代码
            success = startActivity(v, intent, tag);
        } catch (ActivityNotFoundException e) {
            // 没有找到Activity
            Toast.makeText(this, R.string.activity_not_found, Toast.LENGTH_SHORT).show(); 
            Log.e(TAG, "Unable to launch. tag=" + tag + " intent=" + intent, e);
        }
        return success;
    }

Launcher # startActivity()

private boolean startActivity(View v, Intent intent, Object tag) {
        // 添加flag
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        // ... 省略代码

        try{
            startActivity(intent, optsBundle);
            return true;
        } catch(){ 
        }
        return false;
}

下面的分析过程可参考 Activity具体是怎么创建的？又是怎么显示出来的？

Activity # startActivity()

@Override
    public void startActivity(Intent intent, @Nullable Bundle options) {
        if (options != null) {
            startActivityForResult(intent, -1, options);
        } else {
            startActivityForResult(intent, -1);
        }
    }