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从非 UI 线程逐行更新 TextView（通过setText()旧行到新行）的片段：

TextView mLog;
final static String ONE_LINER;

// Condition 1: update from loopless thread
new Thread(new Runnable() {
    @Override
    public void run() {
        mLog.append(ONE_LINER);
    }
}).start();

// Condition 2: update from thread with Looper
HandlerThread handlerThread = new HandlerThread();
handlerThread.start();
Handler handler = new Handler(handlerThread.getLooper()) {
    @Override
    public void handleMessage(Message msg) {
        mLog.append(ONE_LINER);
    }
};
handler.sendEmptyMessage();

代码执行会导致具有不同堆栈跟踪的CalledFromWrongThreadException（请检查下面的“Stacktrace #1”和“Stacktrace #2”）。在这两种变体下（从普通的无循环线程或从内部有 Looper 的HandlerThread更新视图）异常抛出并不精确——事件不会在每次通过工作线程更新 UI 后准确发生。

有没有人想过为什么具有以下调用例程的系统行为（在相同的输入条件下）不是持久的？

Stacktrace #1（频率：高；大多数时候）

android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
            at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:7900)
            at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:1207)
            at android.view.ViewGroup.invalidateChild(ViewGroup.java:5424)
            at android.view.View.invalidateInternal(View.java:13884)
            at android.view.View.invalidate(View.java:13848)
            at android.view.View.invalidate(View.java:13832)
            at android.widget.TextView.updateAfterEdit(TextView.java:8918)
            at android.widget.TextView.handleTextChanged(TextView.java:8943)
            at android.widget.TextView$ChangeWatcher.onTextChanged(TextView.java:11623)
            at android.text.SpannableStringBuilder.sendTextChanged(SpannableStringBuilder.java:1037)
            at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:563)
            at android.text.SpannableStringBuilder.append(SpannableStringBuilder.java:286)
            at android.text.SpannableStringBuilder.append(SpannableStringBuilder.java:34)
            at android.widget.TextView.append(TextView.java:4454)
            at android.widget.TextView.append(TextView.java:4441)

Stacktrace #2（频率：罕见；捕获一次）

android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
            at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:7900)
            at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:1170)
            at android.view.View.requestLayout(View.java:20043)
            at android.view.View.requestLayout(View.java:20043)
            at android.view.View.requestLayout(View.java:20043)
            at android.view.View.requestLayout(View.java:20043)
            at android.view.View.requestLayout(View.java:20043)
            at android.view.View.requestLayout(View.java:20043)
            at android.view.View.requestLayout(View.java:20043)
            at android.widget.TextView.checkForRelayout(TextView.java:8024)
            at android.widget.TextView.setText(TextView.java:4959)
            at android.widget.TextView.setText(TextView.java:4786)
            at android.widget.TextView.append(TextView.java:4451)
            at android.widget.TextView.append(TextView.java:4441)

注意：

  1. 没有错误“只有创建视图层次结构的原始线程可以触摸它的视图”当视图更新时没有延迟说明并没有完全涵盖问题（仅“Stacktrace #2”）。
  2. 操作系统：安卓6.0。
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