TreeView

Android TreeView is used to display data in tree structures.

Overview

The library is designed to support different algorithms. Currently, only the algorithm from Walker (with the runtime improvements from Buchheim) has been implemented. Feel free to contribute. The algorithm should only implement the Algorithm Interface.

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dependencies {
    implementation 'de.blox.treeview:treeview:0.1.0'
}

Usage

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <de.blox.treeview.TreeView
     android:id="@+id/treeview"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
    </de.blox.treeview.TreeView>
</LinearLayout>

You can make the node Layout how you like. Just define a layout file, e.g. node.xml ...

<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
                                    xmlns:card_view="http://schemas.android.com/apk/res-auto"
                                    android:id="@+id/card_view"
                                    android:layout_width="match_parent"
                                    android:layout_height="wrap_content"
                                    android:layout_gravity="center"
                                    android:layout_margin="5dp"
                                    card_view:cardBackgroundColor="@android:color/holo_blue_dark"
                                    card_view:cardElevation="16dp"
                                    card_view:contentPadding="10dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="@android:color/white"
            android:textStyle="bold"/>

    </LinearLayout>
</android.support.v7.widget.CardView>

... and use it with the adapter

public class MainActivity extends AppCompatActivity {
    private int nodeCount = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TreeView treeView = findViewById(R.id.tree);

        BaseTreeAdapter adapter = new BaseTreeAdapter<ViewHolder>(this, R.layout.node) {
            @NonNull
            @Override
            public ViewHolder onCreateViewHolder(View view) {
                return new ViewHolder(view);
            }

            @Override
            public void onBindViewHolder(ViewHolder viewHolder, Object data, int position) {
                viewHolder.mTextView.setText(data.toString());
            }
        };
        treeView.setAdapter(adapter);
        
        // example tree
        TreeNode rootNode = new TreeNode(getNodeText());
        rootNode.addChild(new TreeNode(getNodeText()));
        final TreeNode child3 = new TreeNode(getNodeText());
        child3.addChild(new TreeNode(getNodeText()));
        final TreeNode child6 = new TreeNode(getNodeText());
        child6.addChild(new TreeNode(getNodeText()));
        child6.addChild(new TreeNode(getNodeText()));
        child3.addChild(child6);
        rootNode.addChild(child3);
        final TreeNode child4 = new TreeNode(getNodeText());
        child4.addChild(new TreeNode(getNodeText()));
        child4.addChild(new TreeNode(getNodeText()));
        rootNode.addChild(child4);

        adapter.setRootNode(rootNode);
    }
    
    private String getNodeText() {
        return "Node " + nodeCount++;
    }
}

ViewHolder class:

    private class ViewHolder {
        TextView mTextView;
        ViewHolder(View view) {
            mTextView = view.findViewById(R.id.textView);
        }
    }

Customization

To use the custom attributes you have to add the namespace first: xmlns:app="http://schemas.android.com/apk/res-auto"

Attribute	Format	Example	Explanation
levelSeparation	Dimension	50dp	How much space should be used between levels
lineThickness	Dimension	10dp	Set how thick the connection lines should be
lineColor	Color	"@android:color/holo_red_dark"	Set the color of the connection lines
useMaxSize	Boolean	true	Use the same size for each node

GitHub