冷知识——解决模态框弹框破坏沉浸式全屏模式

[soapgu]

• 妖孽的bug

目前把安卓的App的界面以全屏模式现实，不现实上方状态栏和下方的导航栏已经没有问题。一次无意的操作发现，突然上方的状态栏出现了。后经过反正验证，发现和模态框有关，一开始并没多在意，以为是个别样式设置问题。后面发现只要是模态框就会破坏全屏沉浸式模式。

• 问题解决定位

这个问题比较棘手，官网似乎并没有提到。属于小小冷门，百度出的解决方案也是语焉不详，想这种解决针对性问题还是StackOverflow最靠谱

How do I maintain the Immersive Mode in Dialogs?

• 相关代码

1. 原生Dialog的相关处理

/**
 * 模态框相关方法
 */
public abstract class DialogFns {

    /**
     * 沉浸式显示模态框
     * @param dialog 模态框
     * @param context 当前调用端Activity
     */
    public static void showImmersive(Dialog dialog, Activity context){
        //Here's the magic..
        //Set the dialog to not focusable (makes navigation ignore us adding the window)
        dialog.getWindow().setFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE, WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE);

        //Set the dialog to immersive
        dialog.getWindow().getDecorView().setSystemUiVisibility(
                context.getWindow().getDecorView().getSystemUiVisibility());

        //Show the dialog! (Hopefully no soft navigation...)
        dialog.show();

        //Clear the not focusable flag from the window
        dialog.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE);
    }
}

调用部分

AlertDialog exitDialog = new AlertDialog.Builder(this.requireContext())
                    .setTitle("退出")
                    .setMessage("请确认是否退出")
                    .setPositiveButton("是", (dialog, which) -> {
                        dialog.dismiss();
                        Context context = requireContext();
                        context.sendBroadcast(new Intent("com.android.systemui.SHOW_NAVIGATION_BAR"));
                        context.sendBroadcast(new Intent("com.android.showNavBar"));
                        String packageName = this.requireContext().getPackageName();
                        String command = String.format("am force-stop %s", packageName);
                        Logger.w("-----this application %s will be killed----", packageName);
                        ShellFns.excuteSlient(command);
                    })
                    .setNegativeButton("否", null)
                    .create();
            //exitDialog.show();
            DialogFns.showImmersive( exitDialog,requireActivity() );

2. DialogFragment的处理

DialogFragment的内部实现也是Dialog，原理上是一样的，代码处理不同。

public class MVVMDialogFragment<VM extends ViewModel> extends DialogFragment {
    ...

    /**
     * 设置是否沉浸模式，默认是
     * 派生类可以改写此方法
     * @return 是否全屏
     */
    protected boolean showImmersive(){
        return true;
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        if( showImmersive() ) {
            requireDialog().getWindow().setFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE, WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE);
            requireDialog().getWindow().getDecorView().setSystemUiVisibility(requireActivity().getWindow().getDecorView().getSystemUiVisibility());

            requireDialog().setOnShowListener(dialog -> {
                //Clear the not focusable flag from the window
                requireDialog().getWindow().clearFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE);
            });
        }
        ...
    }
}

• 总结部分

代码重点就是

• 把Dialog对应的Window设置上FLAG_NOT_FOCUSABLE标记
• setSystemUiVisibility和当前的的Activity的值一模一样
• 调用show
• show调用完成后，把 FLAG_NOT_FOCUSABLE标记取消

经过测试可行