Java / Android的基本问题

Question

I started learning java a few days ago, so I'm quite lost with it. I want to show a text received from an intent and make it look like this: "You've written : ." It isn't working at all and I'm only able to show the text from the intent.

Here's my code:

// Create the text view
TextView textView = new TextView(this);
textView.setTextSize(40);
System.out.print("You've written: ");
textView.setText(message);
System.out.print(".");

// Set the text view as the activity layout
setContentView(textView);
}

Besides, I'm trying to display the text written above in the first line of the page (or as many lines it takes) and, below, a label to insert a text together with a Button. The problem is that I can only see the text from the intent. Here's my code:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".DisplayMessageActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <EditText android:id="@+id/edit_message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="@string/edit_message" />

    <Button 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send"
        android:onClick="sendMessage"/>

</RelativeLayout>

Thankyou very much, I wish I'll be answered soon.

Answer 1

Instead of System.out.println.

Do like this.

<TextView
    android:id="@+id/topTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

and Get the view in activity.

public void onCreate(Bundle bundle) {
    .........
   setContentView(layout_xml);
   TextView textView = (TextView)findViewById(R.id.topTextView);
   textView.setText("You've written: " + message + " .");
   .........

}

Answer 2

If you are trying to reference the TextView inside your layout it needs to referenced in the Activity. The above solution shows you how to handle that. setContentView(R.layout.file_name) is what should be used to reference a layout created inside an xml file stored in res/layout/file_name.xml or created manually inside your code. If you are going to call setContentView for a layout contructed inside your (Activity) it will take some more code. If the message is all is need to be displayed you can always call Toast.maketText(Context, message, Toast.LENGTH_SHORT).show(); for example. The other suggestion is Java developers are used to using System.out.println() to debug to the console. In Android they have a neat feature we use called LogCat that can display messages going on inside your code by saying (example for debugging purposes) Log.d(TAG, message); Where TAG is usually a constant defined for the Activity,Fragment, etc. you are in so you can see where the message is coming from and display whatever value you normally would have used in System.out.println().