单击按钮后，Android背景图像消失

Question

Very new to Android development. I have a training app that has a text input field and a button. If the entered text matches a word, then the button click creates a new page (Intent?) which displays some text.

The problem I'm having is that the new page that is created by the button click does not have the same background image as the main page. I don't know why. Here's the relevant bits of code I have so far. I can post more if required.

**fragment_welcome_screen.xml**

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="horizontal"
    android:background="@drawable/bg_pic">
    <EditText android:id="@+id/edit_message"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/edit_message"
        android:layout_weight="1"/>

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

This part works fine and bg_pic is displayed.

WelcomeScreen.java

public void sendMessage(View view) {
        // Do something in response to button

        EditText editText = (EditText) findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        if ((message.equals("Secret"))||(message.equals("secret"))) {
            Intent intent = new Intent(this,
                    DisplayMessageActivity.class);
            intent.putExtra(EXTRA_MESSAGE, message);
            startActivity(intent);
        }

    }

I want the button to work only if "Secret" is typed in.

DisplayMessageActivity.java


public class DisplayMessageActivity extends Activity {

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

        // Get the message from the intent
        Intent intent = getIntent();
        //String message = intent.getStringExtra(WelcomeScreen.EXTRA_MESSAGE);
        String message = "Test String";
        TextView textView = new TextView(this);
        textView.setTextSize(24);
        textView.setText(message);

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

I know I'm probably doing something wrong here.

activity_display_message.xml


<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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:background="@drawable/test_pic"
    tools:context="com.example.varun.myapplication.DisplayMessageActivity">

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

</RelativeLayout>

I would expect test_pic to be the background of the page that is displayed when the button is pressed. But its not. The background is just white.

I realize this is probably a trivial question but can someone please help me out? I would really appreciate it.

Thank you.

Answer 1

Why you used setContentView() 2 times in DisplayMessageActivity.java. Remove the secound setcontentview() and assign some id for the textview in activity_display_message.xml. Here is the code to assign id for textview.

<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:background="@drawable/test_pic"
            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="com.example.varun.myapplication.DisplayMessageActivity">

<TextView
    android:id="@+id/mytv"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/test_pic"
    android:text="@string/hello_world"/>

And get the textview with that id reference like

TextView textView = (TextView)findViewById(R.id.mytv);

And use this textview reference to show message from the previous activity like this

textView.setText(message);

I hope this will helpful for you.

Answer 2

Change code

public class DisplayMessageActivity extends Activity {

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

        // Get the message from the intent
        Intent intent = getIntent();
        //String message = intent.getStringExtra(WelcomeScreen.EXTRA_MESSAGE);
        String message = "Test String";
        TextView textView = (TextView)findViewByID(R.id.textMessage)
        textView.setTextSize(24);
        textView.setText(message);
        }

and also put id for textview

<TextView android:id="@+id/textMessage"
  android:text="@string/hello_world" android:layout_width="wrap_content"
  android:layout_height="wrap_content" android:background="@drawable/test_pic"/>

Answer 3

删除此setContentView（textView）;

Answer 4

Why you have wrote setContentView(textView); line?

Just remove above given line of the code, and you are done.

Answer 5

try like this,

<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:paddingLeft="@dimen/activity_horizontal_margin"
        android:paddingRight="@dimen/activity_horizontal_margin"
        android:paddingTop="@dimen/activity_vertical_margin"
        android:paddingBottom="@dimen/activity_vertical_margin"
        android:background="@drawable/test_pic"
        tools:context="com.example.varun.myapplication.DisplayMessageActivity">

        <TextView android:id="@+id/txtmsg"
            android:text="@string/hello_world" android:layout_width="wrap_content"
            android:layout_height="wrap_content" android:background="@drawable/test_pic"/>

    </RelativeLayout>


    public class DisplayMessageActivity extends Activity {

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

            // Get the message from the intent
            Intent intent = getIntent();
            //String message = intent.getStringExtra(WelcomeScreen.EXTRA_MESSAGE);
            String message = "Test String";
            TextView textView = (TextView) findViewById(R.id.txtmsg);
            textView.settext(message);
        }