Question

我知道从工作线程访问UI视图是非法的。例如，下面的代码在Android 4.4 (API 19)上引发异常：android.view.ViewRootImpl$CalledFromWrongThreadException：只有创建视图层次结构的原始线程才能触摸其视图。

但是，它可以在Android 8.0 (API 26)上正常运行，并且可以成功更新TextView。问题是-为什么？

也许可以在新的Android版本中从另一个线程访问视图？

public class TestActivity extends AppCompatActivity {

    private Button btnStart;
    private TextView txtInfo;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);

        txtInfo = (TextView) findViewById(R.id.txtInfo);
        btnStart = (Button) findViewById(R.id.btnStart);

        btnStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Thread t = new Thread(new Runnable() {
                    @Override public void run() {
                        for (int i = 0; i < 10; i++) {
                            try {
                                Thread.sleep(1000);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            txtInfo.setText(String.valueOf(i + 1));
                        }
                    }
                });
                t.start();
            }
        });
    }
}

Answer 1

来自the post

<块引用>

@Override
public final void invalidateChild(View child, final Rect dirty) {
    final AttachInfo attachInfo = mAttachInfo;
    if (attachInfo != null && attachInfo.mHardwareAccelerated) {
        // HW accelerated fast path
        onDescendantInvalidated(child, child); // <-- does not have thread check
        return;
    }
    // A bunch of code here for old slow path
    parent.invalidateChildInParent(location, dirty); // <-- has thread check
}

后来修复了：https://android-review.googlesource.com/c/platform/frameworks/base/+/937477

为什么可以从Android 8.0中的辅助线程访问视图？

1 个答案: