Angular Material 6.4.7 Tree default opened by expand all [duplicate]

Question

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Angular Material 6.0.1 Tree default opened and expand/collapse all (2 answers)

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I'm using the Angular Material Tree in my project. Is it possible to have the tree opened by default.

I'm using the last example via Tree with partially loaded data: https://stackblitz.com/angular/pyyaxgjpqnn?file=app%2Ftree-loadmore-example.ts

Thanks for your help.

I tried this solution but I have this error : ERROR Error: "ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Previous value: 'aria-expanded: false'. Current value: 'aria-expanded: true'."

    ngAfterViewInit() {
      this.treeControl.expandAll();
    }

Answer 1

for whatever reason the nestedTreeControl.dataNodes does not get updated properly. update it with the same data you used for the nestedDataSource and it should work.

 this.store.select(r => entity).subscribe(r => {
        this.nestedDataSource.data = [new Entity(JSON.parse(JSON.stringify(r)))];
        this.nestedTreeControl.dataNodes = this.nestedDataSource.data;
        this.nestedTreeControl.expandAll();
      })