android studio Recyclerview sample 筆記

先看  MainActivity

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

    if (savedInstanceState == null) {
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        RecyclerViewFragment fragment = new RecyclerViewFragment();
        transaction.replace(R.id.sample_content_fragment, fragment);
        transaction.commit();
    }

}

在activity_main.xml 裡面有個frame_layout

<FrameLayout      android:id="@+id/sample_content_fragment"      android:layout_weight="2"      android:layout_width="match_parent"      android:layout_height="0px" />


接下來看   RecyclerViewFragment


public class RecyclerViewFragment extends Fragment {


   @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Initialize dataset, this data would usually come from a local content provider or    // remote server.    initDataset();
}

}


//  初始化  mDataset string array

private void initDataset() {
    mDataset = new String[DATASET_COUNT];
    for (int i = 0; i < DATASET_COUNT; i++) {
        mDataset[i] = "This is element #" + i;
    }
}



@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.recycler_view_frag, container, false);
    rootView.setTag(TAG);

    // BEGIN_INCLUDE(initializeRecyclerView)    mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerView);

    // LinearLayoutManager is used here, this will layout the elements in a similar fashion    // to the way ListView would layout elements. The RecyclerView.LayoutManager defines how    // elements are laid out.    mLayoutManager = new LinearLayoutManager(getActivity());

    mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;

    if (savedInstanceState != null) {
        // Restore saved layout manager type.        mCurrentLayoutManagerType = (LayoutManagerType) savedInstanceState
                .getSerializable(KEY_LAYOUT_MANAGER);
    }
    setRecyclerViewLayoutManager(mCurrentLayoutManagerType);

    mAdapter = new CustomAdapter(mDataset);
    // Set CustomAdapter as the adapter for RecyclerView.    mRecyclerView.setAdapter(mAdapter);
    // END_INCLUDE(initializeRecyclerView)
    mLinearLayoutRadioButton = (RadioButton) rootView.findViewById(R.id.linear_layout_rb);
    mLinearLayoutRadioButton.setOnClickListener(new View.OnClickListener() {
        @Override        public void onClick(View v) {
            setRecyclerViewLayoutManager(LayoutManagerType.LINEAR_LAYOUT_MANAGER);
        }
    });

    mGridLayoutRadioButton = (RadioButton) rootView.findViewById(R.id.grid_layout_rb);
    mGridLayoutRadioButton.setOnClickListener(new View.OnClickListener() {
        @Override        public void onClick(View v) {
            setRecyclerViewLayoutManager(LayoutManagerType.GRID_LAYOUT_MANAGER);
        }
    });

    return rootView;
}


recycler_view_frag.xml 內容如下: 有一個 LinearLayout....裡面包含著一個  <android.support.v7.widget.RecyclerView


<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">
    <RadioGroup        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:gravity="center_horizontal"        android:orientation="horizontal"        android:checkedButton="@+id/linear_layout_rb">
        <RadioButton android:id="@+id/linear_layout_rb"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="@string/linear_layout_manager"/>
        <RadioButton android:id="@+id/grid_layout_rb"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="@string/grid_layout_manager"/>
    </RadioGroup>

    <android.support.v7.widget.RecyclerView        android:id="@+id/recyclerView"        android:layout_width="match_parent"        android:layout_height="match_parent"/>
</LinearLayout>


 
再回去看  RecyclerViewFragment

// LinearLayoutManager is used here, this will layout the elements in a similar fashion// to the way ListView would layout elements. The RecyclerView.LayoutManager defines how// elements are laid out.mLayoutManager = new LinearLayoutManager(getActivity());

mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;


if (savedInstanceState != null) {
    // Restore saved layout manager type.    mCurrentLayoutManagerType = (LayoutManagerType) savedInstanceState
            .getSerializable(KEY_LAYOUT_MANAGER);
}
setRecyclerViewLayoutManager(mCurrentLayoutManagerType);


mAdapter = new CustomAdapter(mDataset);
// Set CustomAdapter as the adapter for RecyclerView.mRecyclerView.setAdapter(mAdapter);
// END_INCLUDE(initializeRecyclerView)

//  設下去就變成   LINEAR_LAYOUT_MANAGER
mLinearLayoutRadioButton = (RadioButton) rootView.findViewById(R.id.linear_layout_rb);
mLinearLayoutRadioButton.setOnClickListener(new View.OnClickListener() {
    @Override    public void onClick(View v) {
        setRecyclerViewLayoutManager(LayoutManagerType.LINEAR_LAYOUT_MANAGER);
    }
});

// 設下去就變成gridlayout
mGridLayoutRadioButton = (RadioButton) rootView.findViewById(R.id.grid_layout_rb);
mGridLayoutRadioButton.setOnClickListener(new View.OnClickListener() {
    @Override    public void onClick(View v) {
        setRecyclerViewLayoutManager(LayoutManagerType.GRID_LAYOUT_MANAGER);
    }
});

return rootView;

}


public void setRecyclerViewLayoutManager(LayoutManagerType layoutManagerType) {
    int scrollPosition = 0;

    // If a layout manager has already been set, get current scroll position.    if (mRecyclerView.getLayoutManager() != null) {
        scrollPosition = ((LinearLayoutManager) mRecyclerView.getLayoutManager())
                .findFirstCompletelyVisibleItemPosition();
    }

    switch (layoutManagerType) {
        case GRID_LAYOUT_MANAGER:
            mLayoutManager = new GridLayoutManager(getActivity(), SPAN_COUNT);
            mCurrentLayoutManagerType = LayoutManagerType.GRID_LAYOUT_MANAGER;
            break;
        case LINEAR_LAYOUT_MANAGER:
            mLayoutManager = new LinearLayoutManager(getActivity());
            mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
            break;
        default:
            mLayoutManager = new LinearLayoutManager(getActivity());
            mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
    }

    mRecyclerView.setLayoutManager(mLayoutManager);
    mRecyclerView.scrollToPosition(scrollPosition);
}


重點就是上面那兩行....  利用  setLayoutManager(mLayoutManager);  來變成linear 或是  gridlayout




再來看

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {


裡面又包含著一個 ViewHolder的類別

public static class ViewHolder extends RecyclerView.ViewHolder {
    private final TextView textView;

    public ViewHolder(View v) {
        super(v);
        // Define click listener for the ViewHolder's View.        v.setOnClickListener(new View.OnClickListener() {
            @Override            public void onClick(View v) {
                Log.d(TAG, "Element " + getAdapterPosition() + " clicked.");
            }
        });
        textView = (TextView) v.findViewById(R.id.textView);
    }

    public TextView getTextView() {
        return textView;
    }
}

//  建構子

public CustomAdapter(String[] dataSet) {
    mDataSet = dataSet;
}

// BEGIN_INCLUDE(recyclerViewOnCreateViewHolder)// Create new views (invoked by the layout manager)@Overridepublic ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
    // Create a new view.    View v = LayoutInflater.from(viewGroup.getContext())
            .inflate(R.layout.text_row_item, viewGroup, false);

    return new ViewHolder(v);
}