android - 在获得任何数据之前设置分配变量

Question

翻转扔草动态壁纸后，我找到了这段代码——它创建了草叶网格并设置了索引：

private void createMesh() {
    mVertexBuffer = new ScriptField_Vertex(mRS, mVerticies * 2);

    final Mesh.AllocationBuilder meshBuilder = new Mesh.AllocationBuilder(mRS);
    meshBuilder.addVertexAllocation(mVertexBuffer.getAllocation());

    mBladesIndicies = Allocation.createSized(mRS, Element.U16(mRS), mIndicies);
    meshBuilder.addIndexSetAllocation(mBladesIndicies, Primitive.TRIANGLE);

    mBladesMesh = meshBuilder.create();

    short[] idx = new short[mIndicies];
    int idxIdx = 0;
    int vtxIdx = 0;
    for (int i = 0; i < mBladeSizes.length; i++) {
        for (int ct = 0; ct < mBladeSizes[i]; ct ++) {
            idx[idxIdx + 0] = (short)(vtxIdx + 0);
            idx[idxIdx + 1] = (short)(vtxIdx + 1);
            idx[idxIdx + 2] = (short)(vtxIdx + 2);
            idx[idxIdx + 3] = (short)(vtxIdx + 1);
            idx[idxIdx + 4] = (short)(vtxIdx + 3);
            idx[idxIdx + 5] = (short)(vtxIdx + 2);
            idxIdx += 6;
            vtxIdx += 2;
        }
        vtxIdx += 2;
    }

    mBladesIndicies.copyFrom(idx);
}

meshBuilder.addIndexSetAllocation(mBladesIndicies, Primitive.TRIANGLE);我对这两条线感到困惑：mBladesIndicies.copyFrom(idx); 为什么他们在变量实际获取他的数据mBladesIndicies之前将其发送给网格构建器并创建网格mBladesIndiciesmBladesIndicies.copyFrom(idx);

简而言之 -为什么meshBuilder.addIndexSetAllocation(mBladesIndicies, Primitive.TRIANGLE);来mBladesMesh = meshBuilder.create();之前？ mBladesIndicies.copyFrom(idx);

Answer 1

分配通过引用而不是副本连接到网格。因此，添加数据的顺序无关紧要。

Mesh.Builder 在创建后会保留分配引用。