Android Presentation 类 - 如何动态更改 Presentation View

Question

我的演示文稿终于成功了。我的第一个屏幕有一个主要的 activity，第二个屏幕有一个 Presentation。我的问题是，我无法更改演示 View 中的内容。

为什么我不能在第二个屏幕上显示演示文稿后更改 TextView？在 MainActivity 中调用方法 changeText("Test123") 会使我的应用程序崩溃。

public class MainActivity extends Activity {

    private PresentationActivity presentationActivity;

    protected void onCreate(Bundle savedInstanceState) {    

        super.onCreate(savedInstanceState);  


        // init Presentation Class

        DisplayManager displayManager = (DisplayManager) this.getSystemService(Context.DISPLAY_SERVICE);
        Display[] presentationDisplays = displayManager.getDisplays(DisplayManager.DISPLAY_CATEGORY_PRESENTATION);
        if (presentationDisplays.length > 0) {
            // If there is more than one suitable presentation display, then we could consider
            // giving the user a choice.  For this example, we simply choose the first display
            // which is the one the system recommends as the preferred presentation display.
            Display display = presentationDisplays[0];
            PresentationActivity presentation = new PresentationActivity(this, display);
            presentation.show();

            this.presentationActivity =  presentation;    
        }
    }

    public void changeText (String s) {

        this.presentationActivity.setText(s);

    }
}



public class PresentationActivity extends Presentation {

    private TextView text;



    private PresentationActivity presentation;


public PresentationActivity(Context outerContext, Display display) {
    super(outerContext, display);
    // TODO Auto-generated constructor stub

}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);     

    setContentView(R.layout.activity_presentation);   

    TextView text = (TextView) findViewById(R.id.textView1);

    this.text = text;
    // works fine:
    text.setText("test");      

}

public void setText(String s){

    // error
    this.text.setText(s);

}

Answer 1

好吧，我查看了 LogCat。异常(exception)是:

E/AndroidRuntime(13950): android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

我的 MainActivity 中的代码在另一个线程上运行。要从此处进行 UI 工作，我需要使用 runOnUiThread。我在 this 中找到了这个解决方案回答。

我的 changeText 方法现在看起来像这样:

public void changeText (String s) {

        runOnUiThread(new Runnable() {
          public void run() {
              presentationActivity.setImageView(position);
          }
    });
}

感谢您的帮助!现在我知道如何使用 LogCat 来做类似的事情了。