如何以编程方式向片段添加按钮 [英] How to add a button programmatically to a fragment

问题描述

我无法以编程方式向片段添加按钮.(按钮的数量是可变的)

I can't manage to add programmatically a button to a fragment. (The number of buttons is variable)

我尝试使用一个" addView方法将按钮添加到rootView，但是没有一个.

I tried to add the button to the rootView with "an" addView method, but there isn't one.

我尝试在膨胀按钮之前将按钮添加到布局中，但是我不知道如何获取布局:(类型为id的预期资源错误)

I tried to add the button to the layout before inflating it, but I don't know how to get the layout : (Expected resource of type id error)

RelativeLayout rl = getView().findViewById(R.layout.fragment_main);

但是当充气机充气时，资源是好的.

But when the inflater inflates it, the resource is good.

我尝试将按钮添加到"onViewCreated"方法中，但是findViewById(R.layout.fragment_main)遇到了同样的问题，告诉我有一个错误(ID类型的预期资源).

I tried to add the button in the "onViewCreated" method, but I got the same problem with findViewById(R.layout.fragment_main) telling me there is an error (Expected resource of type id).

当我创建这样的按钮时:

When I create a button like this :

Button bt = new Button(this);

此"不是有效的上下文.不知道该用什么.

"this" is not a valid context. Don't know what to use instead.

那么，我该如何实现呢?

So, how can I achieve it ?

基本代码:

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment())
                .commit();
    }
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@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();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        return rootView;
    }
}
}

Activity_main.xml

Activity_main.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    tools:ignore="MergeRootFrame" />

Fragment_main.xml

Fragment_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity$PlaceholderFragment">

    <TextView
        android:text="@string/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</RelativeLayout>

推荐答案

在fragment_main.xml上，您的代码中有几处需要纠正:

There are a few thing to correct in your code, on the fragment_main.xml:

如果要访问xml上的元素，则需要为其赋予唯一的ID.对于您的相对布局，您会丢失它，因此您将无法在片段视图中找到它.

If you want to access an element on an xml, you need to give it a unique id. In the case of your relative layout you are missing it and therefore you won't be able to find it on the fragment view.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/fragment_main_layout"     <!--some id-->
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity$PlaceholderFragment">

    <TextView
        android:text="@string/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</RelativeLayout>

现在在您的片段类中可以找到它！

Now in your fragment class you can find it!

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_main, container, false);

    //Find the layout with the id you gave in on the xml
    RelativeLayout rl = (RelativeLayout) rootView.findViewById(R.id.fragment_main_layout);

   //And now you can add the buttons you need, because it's a fragment, use getActivity() as context
   Button bt = new Button(getActivity());
   //You can add LayoutParams to put the button where you want it and the just add it
   rl.addView(bt);


    return rootView;
}

就是这样，您的布局上有了一个新按钮

And that's it, you have a new button on your layout

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