Question

I am using Handler to make the UI responsive when doing search. I used Handler but why it still displays the error “Only the original thread that created a view hierarchy can touch its views”.

@Override
public void onClick(final View view) {
    if (view.getId() == R.id.searchButton) {
        processThread(searchEditText.getText().toString());
    }
}

private void processThread(final String word) {
    progressDialog.show();

    new Thread() {
        @Override
        public void run() {

            // This is a long time method.
            searchWord(word);

            searchHandler.sendEmptyMessage(0);
        };
    }.start();
}

private void searchWord(final String word) {
    final String result = dictionaryClient.lookup(word);
    resultTextView.setText(result);
}

private final Handler searchHandler = new Handler() {
    @Override
    public void handleMessage(final Message msg) {
        super.handleMessage(msg);
        progressDialog.dismiss();
    };
};


07-04 22:04:54.699: ERROR/AndroidRuntime(8815): android.view.ViewRoot$CalledFromWrongThreadException:
Only the original thread that created a view hierarchy can touch its views.
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.view.ViewRoot.checkThread(ViewRoot.java:2802)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.view.ViewRoot.requestLayout(ViewRoot.java:594)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.view.View.requestLayout(View.java:8125)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.view.View.requestLayout(View.java:8125)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.view.View.requestLayout(View.java:8125)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.view.View.requestLayout(View.java:8125)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.view.View.requestLayout(View.java:8125)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.widget.ScrollView.requestLayout(ScrollView.java:1200)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.view.View.requestLayout(View.java:8125)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.widget.TextView.checkForRelayout(TextView.java:5371)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.widget.TextView.setText(TextView.java:2688)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.widget.TextView.setText(TextView.java:2556)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at android.widget.TextView.setText(TextView.java:2531)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at com.megadict.activity.DictionaryActivity.searchWord(DictionaryActivity.java:135)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at com.megadict.activity.DictionaryActivity.access$1(DictionaryActivity.java:133)
07-04 22:04:54.699: ERROR/AndroidRuntime(8815):     at com.megadict.activity.DictionaryActivity$2.run(DictionaryActivity.java:146)

Edit: I followed this article .

Answer 1

The problem is this line in searchWord:

resultTextView.setText(result);

That needs to be executed on the UI thread but is running in the search thread. Replace it with:

searchHandler.post(new Runnable() {
    @Override
    public void run() {
        resultTextView.setText(result);
    }
});