如何在 Android 中使 View 不可见/Gone onBackPressed() 方法？

Question

我在 Tabhost 中有 5 个活动。 （即 MainActivity.java Home.java、NowReading.java、Favorites.java 和 Profile.java）。在主要活动中，我正在加载 tabhost，如下所示。

public class MainActivity extends TabActivity {
    TabHost tabHost;
    Context context = MainActivity.this;
    TextView txt_Login;
    View homeTabLayout;
    View reviewLayout;

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

        txt_Login = (TextView) findViewById(R.id.txt_Login);
        final Spinner spnrLanguage = (Spinner) findViewById(R.id.spnrLanguage);
        final Spinner spnrBrowseBy = (Spinner) findViewById(R.id.spnrBrowseBy);

        tabHost = getTabHost();

        // Android tab
        Intent intentHome = new Intent().setClass(this, Home.class);
        TabSpec tabSpecHome = tabHost
                .newTabSpec("Home")
                .setIndicator("Home",
                        getResources().getDrawable(R.drawable.home))
                .setContent(intentHome);

        tabHost.addTab(tabSpecHome);

        Intent intentNowReading = new Intent().setClass(this, NowReading.class);
        TabSpec tabSpecNowReading = tabHost
                .newTabSpec("Now Reading")

                .setIndicator("Now Reading",
                        getResources().getDrawable(R.drawable.now_reading))
                .setContent(intentNowReading);
        tabHost.addTab(tabSpecNowReading);

        Intent intentFavourite = new Intent().setClass(this, Favorites.class);
        TabSpec tabSpecFavourite = tabHost
                .newTabSpec("Favourite")
                .setIndicator("Favorites",
                        getResources().getDrawable(R.drawable.favorites))
                .setContent(intentFavourite);
        tabHost.addTab(tabSpecFavourite);

        Intent intentProfile = new Intent().setClass(this, Profile.class);
        TabSpec tabSpecProfile = tabHost
                .newTabSpec("Profile")
                .setIndicator("Profile",
                        getResources().getDrawable(R.drawable.profile))
                .setContent(intentProfile);
        tabHost.addTab(tabSpecProfile);
tabHost.setCurrentTabByTag("Home");

在 Mainactivity.java 中将 Home.java 设置为当前选项卡。作为

tabHost.setCurrentTabByTag("Home");

在 setContentView 中加载布局 home_activity.xml。

这里是 XML 代码

    <?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/frameLayout01"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <RelativeLayout
        android:id="@+id/rel_HomeLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <GridView
            android:id="@+id/gridview"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center"
            android:numColumns="auto_fit"
            android:stretchMode="columnWidth" >
        </GridView>
    </RelativeLayout>

    <ScrollView
        android:id="@+id/scroll_ReviewLayout"
        android:layout_width="fill_parent"
        android:layout_height="match_parent" >

        <RelativeLayout
            android:id="@+id/rel_ReviewLayout01"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" >

            <ImageView
                android:id="@+id/img_OverVuBookCoverPhoto"
                android:layout_width="130dp"
                android:layout_height="165dp"
                android:layout_margin="5dp"
                android:adjustViewBounds="true"
                android:background="@drawable/rounded_image_borders"
                android:paddingLeft="5dp"
                android:paddingRight="5dp"
                android:src="@drawable/book1" />

            <TextView
                android:id="@+id/txt_revwBookTitle"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignTop="@+id/img_OverVuBookCoverPhoto"
                android:layout_marginTop="10dp"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:text="The Basic Doctrine Of Islam"
                android:textColor="@color/White"
                android:textSize="12sp" />

            <TextView
                android:id="@+id/txt_revwAutherName"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txt_revwBookTitle"
                android:layout_marginTop="2dp"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:text="By: Andrew J Newman"
                android:textColor="@color/SkyBlue"
                android:textSize="11sp" />

            <TextView
                android:id="@+id/txt_PublishDate"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txt_revwAutherName"
                android:layout_marginTop="2dp"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:text="Published: July, 30 2007"
                android:textColor="@color/DarkGray"
                android:textSize="11sp" />

            <RatingBar
                android:id="@+id/ratingbar"
                style="?android:attr/ratingBarStyleSmall"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txt_PublishDate"
                android:layout_marginBottom="6dp"
                android:layout_marginTop="6dp"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:isIndicator="false"
                android:numStars="5"
                android:rating="5"
                android:stepSize="1" />

            <Button
                android:id="@+id/btnOpenBook"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignBaseline="@+id/img_OverVuBookCoverPhoto"
                android:layout_below="@+id/ratingbar"
                android:layout_toRightOf="@+id/img_OverVuBookCoverPhoto"
                android:text="Open Book"
                android:textColor="@color/Black"
                android:textSize="13sp" />

            <ImageButton
                android:id="@+id/btnBack"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignBottom="@+id/btnOpenBook"
                android:layout_alignTop="@+id/btnOpenBook"
                android:layout_marginLeft="5dp"
                android:layout_toRightOf="@+id/btnOpenBook"
                android:src="@drawable/pic_btn_back"
                android:textColor="@color/Black"
                android:textSize="14sp" />

            <TextView
                android:id="@+id/txt_BookOverview"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignLeft="@+id/img_OverVuBookCoverPhoto"
                android:layout_below="@+id/img_OverVuBookCoverPhoto"
                android:layout_marginBottom="10dp"
                android:layout_marginTop="20dp"
                android:text="Book Overview"
                android:textColor="@color/White"
                android:textSize="13sp" />

            <TextView
                android:id="@+id/txt_BookOverviewDetails"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_alignLeft="@+id/img_OverVuBookCoverPhoto"
                android:layout_below="@+id/txt_BookOverview"
                android:lineSpacingExtra="4dp"
                android:lines="10"
                android:text="Lorem ipsum dolor sit amet, there was nothing that I can do she was dead, for this reasean I m gonna loose every thing consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat." >
            </TextView>
        </RelativeLayout>
    </ScrollView>

</FrameLayout>

在 Home.java 的 onCreate 方法中，我将 Framelayout 设为不可见/消失（其中包含 Cliked 书的概述）

  public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.home_activity);

        homeTabLayout = findViewById(R.id.rel_HomeLayout);
        reviewLayout = findViewById(R.id.scroll_ReviewLayout);
        reviewLayout.setVisibility(View.GONE);

现在，当我单击任何一本书时，它会使我之前在 onCreat 方法上使用代码不可见/消失的视图可见

gridView.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int pos,
                    long arg3) {
                // TODO Auto-generated method stub

                Toast.makeText(context, BookTitle.get(pos), Toast.LENGTH_SHORT)
                        .show();
                reviewLayout.setVisibility(View.VISIBLE);

注意：这不是新的活动，而是我刚刚在点击事件上创建了一个视图（即 reviewLayout.setVisibility(View.VISIBLE);）。

• 我想让这个视图在 onBackPressed() 方法上不可见/消失。
• 我应该在 MainActivity.java 还是 Home.java 文件中调用此方法？
• 如果我在 MainActivity.java 中调用此方法，则会引发 nullPointerException。

Answer 1

您可以覆盖返回按钮方法

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        // You can call view.setVisiblility(View.GONE) if you want to remove it from the layout, or view.setVisibility(View.INVISIBLE) if you just want to hide it.
        view.setVisiblility(View.GONE); // or view.setVisibility(View.INVISIBLE);
        return true;
    }
    return super.onKeyDown(keyCode, event);
}

Answer 2

您可以覆盖 BackPress 方法... 借助此功能，您可以隐藏您的布局或视图...

@Override
public void onBackPressed() {
     super.onBackPressed();
               // Invisible or Gone Your Views here....
    }