Question

我在fragment.xml中定义了一个布局，在活动中调用.... 当我按下父对象操作栏中的一个按钮时，我想让它显示在onOptionsItemSelected（）中。当我这样做时，它会产生一个空对象引用错误....

fragment.xml之

<RelativeLayout
    android:visibility="invisible"
    android:id="@+id/relative_layout_current_job"
    android:layout_marginTop="5dp"
    android:layout_marginBottom="5dp"
    android:layout_marginLeft="5dp"
    android:layout_marginRight="5dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/text_view_current_job"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/text_current_job"
        android:layout_centerHorizontal="true" />
</RelativeLayout>

MainActivity.java

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

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    if (!mNavigationDrawerFragment.isDrawerOpen()) {
        // Only show items in the action bar relevant to this screen
        // if the drawer is not showing. Otherwise, let the drawer
        // decide what to show in the action bar.
        getMenuInflater().inflate(R.menu.passenger_main, menu);
        restoreActionBar();
        return true;
    }
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_job_confirm) {
        Button b = (Button) findViewById(R.id.action_job_confirm);
        RelativeLayout layoutCurrentJob = (RelativeLayout) findViewById(R.id.relative_layout_current_job);
        TextView status = (TextView) findViewById(R.id.text_view_current_job_status_in_history);
        if((b.getText().toString()) == "job confirm") {
            status.setVisibility(View.INVISIBLE);
            b.setText("Job Started");
            layoutCurrentJob.setVisibility(View.VISIBLE);
        } else {
            status.setVisibility(View.VISIBLE);
            b.setText("jon confirm");
            layoutCurrentJob.setVisibility(View.INVISIBLE);
        }
    }

    return super.onOptionsItemSelected(item);
}

mainmenu.xml

<item 
    android:id="@+id/action_job_confirm" 
    android:title="job confirm"
    app:showAsAction="never"/>

Screenshot

Answer 1

为你的片段做这样的事情：

public class testFragment extends Fragment implements Handler.Callback{

    public final Handler handler = new Handler(testFragment.this);


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        View root = inflater.inflate(R.layout.fragment, container, false);

    }


    @Override
    public boolean handleMessage(Message msg) {
        // TODO Auto-generated method stub

        if (msg.what == 1) {
            //do your job here
        }
        return false;
    }

}

从您的活动中调用它：

testFragment frag = (testFragment) getFragmentManager()
.findFragmentByTag("Fragment_1");

Message ms = Message.obtain(frag.handler,1);
frag.handler.sendMessage(ms);

Answer 2

在您的代码上，初始化

 RelativeLayout layoutCurrentJob=(RelativeLayout) findViewById(R.id.relative_layout_current_job);

错了。因为你想要隐藏/显示的RelativeLayout是你的片段的一部分。你不能用它来初始化RelativeLayout。

它应该如下面片段中的onCreateView

所示

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    View root = inflater.inflate(R.layout.fragment, container, false);
    RelativeLayout layoutCurrentJob=(RelativeLayout) findViewById(R.id.relative_layout_current_job);
}`

您可以通过以下方法

访问Fragment的小部件

RelativeLayout layoutCurrentJob = (RelativeLayout )fragmentobj.getView().findViewById(R.id.img_one));
layoutCurrentJob.setVisibility(View.VISIBLE);

如何在父活动中调用的片段中以编程方式显示布局

2 个答案: