E / MPAndroidChart：无法通过触摸进行选择。没有数据集

Question

Java的：

公共类MainActivity扩展了AppCompatActivity {     私有静态最终字符串DEFAULT_DRIVER =“ oracle.jdbc.driver.OracleDriver”;     私有静态最终字符串DEFAULT_URL =“ jdbc：oracle：thin：@ info706.cwwvo42siq12.ap-southeast-2.rds.amazonaws.com：1521：ORCL”;     私有静态最终字符串DEFAULT_USERNAME =“用户名”;     私有静态最终字符串DEFAULT_PASSWORD =“密码”;

<mat-tree [dataSource]="nestedDataSource" [treeControl]="nestedTreeControl" class="example-tree">

<mat-tree-node *matTreeNodeDef="let node">
  <li class="mat-tree-node">
    <span *ngFor="let item of getArrayForIndenting(node)">&nbsp;&nbsp;&nbsp;&nbsp;</span>
    <button mat-icon-button disabled></button>
    {{ node.name }}: {{ node.value }}
  </li>
</mat-tree-node>

<mat-nested-tree-node *matTreeNodeDef="let node; when: hasNestedChild">
  <div class="mat-tree-node">
    <span *ngFor="let item of getArrayForIndenting(node)">&nbsp;&nbsp;&nbsp;&nbsp;</span>
    <button mat-icon-button matTreeNodeToggle>
      <mat-icon class="mat-icon-rtl-mirror">
        {{ nestedTreeControl.isExpanded(node) ? 'expand_more' : 'chevron_right' }}
      </mat-icon>
    </button>
    {{ node.name }}
  </div>
  <ul [class.example-tree-invisible]="!nestedTreeControl.isExpanded(node)">
    <ng-container matTreeNodeOutlet></ng-container>
  </ul>
</mat-nested-tree-node>

}