Question

我有一个片段，想要隐藏并显示一个按钮。我使用这段代码：

 public class Tablo extends FragmentActivity{
Fragment fg ;
Button click ;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_tablo);
    fg = getFragmentManager().findFragmentById(R.id.emojicons);
    click = (Button) findViewbyId(R.id.Button1);
    click.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            FragmentManager fm = getFragmentManager();
            fm.beginTransaction()
                    .setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out)
                    .show(fg)
                    .commit();
        }
    });

记录错误：

 java.lang.NullPointerException: Attempt to write to field 'int android.app.Fragment.mNextAnim' on a null object reference
        at android.app.BackStackRecord.run(BackStackRecord.java:809)
        at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
        at android.app.FragmentManagerImpl$1.run(FragmentManager.java:452)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:145)
        at android.app.ActivityThread.main(ActivityThread.java:6145)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)

Xml片段：

<fragment
    android:id="@+id/emojicons"
    android:layout_width="match_parent"
    android:layout_height="220dp"
    class="ir.m.sh.textsticker.PlusOneFragment"/>

我的片段：

Android Studio PLusOneFragment

怎么了？

我希望展示和隐藏这个片段并进行测试但是......

Answer 1

我猜你的片段对象是null。试试这样：

PLusOneFragment fg ;
Button click ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tablo);
if(savedInstanceState == null)
    fg = new PLusOneFragment();
else
    fg = getFragmentManager().findFragmentById(R.id.emojicons);
click = (Button) findViewbyId(R.id.Button1);
click.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        FragmentManager fm = getFragmentManager();
        fm.beginTransaction()
                .setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out)
                .show(fg)
                .commit();
    }
});

或者如果你想要，你可以使用Fragment对象而不是PLusOneFragment对象，然后在初始化它时你可以像这样初始化它：片段fg; fg = new PLusOneFragment（）; （其中savedInstanceState为null）;

在android中隐藏show fragment

1 个答案: