Problemas ao Instaciar Telas no Android Studio

thiagodbonis · Maio 25, 2017, 4:31pm

Contenho as seguintes telas no projeto:

AboutScreen.java - about_screen.xml

CameraOverlayBooks.java - camera_overlay_books.xml

A tela “CameraOverlayBooks.java” na verdade é uma tela que é a camera ligada do celular do usuário.
Nela eu inseri um button para poder voltar a tela AboutScreen.java.

O que está acontecendo é o seguinte:

Inseri Intent na tela AboutScreen.java, porém nada acontece ao clicar no botão da tela CameraOverlayBooks. Nem mesmo uma mensagem de errro.

Segue os códigos abaixo:

AboutScreen.java

package com.vuforia.samples.Books.ui.ActivityList;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import com.vuforia.samples.Books.R;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.TextView;

public class AboutScreen extends Activity implements OnClickListener
{
private static final String LOGTAG = “AboutScreen”;

private Button mStartButton;
private String mClassToLaunch;
private String mClassToLaunchPackage;


@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.about_screen);
    
    Bundle extras = getIntent().getExtras();
    mClassToLaunchPackage = getPackageName();
    mClassToLaunch = mClassToLaunchPackage + "." + extras.getString("ACTIVITY_TO_LAUNCH");

    mStartButton = (Button) findViewById(R.id.button_start);
    mStartButton.setOnClickListener(this);

}


// Starts the chosen activity
private void startARActivity()
{
    Intent i = new Intent();
    i.setClassName(mClassToLaunchPackage, mClassToLaunch);
    startActivity(i);
}

@Override
public void onClick(View v)
{
    switch (v.getId())
    {
        case R.id.button_start:
            startARActivity();
            break;
    }
}

}

AboutScreen.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/white"
    android:name="AboutScreen">

    <TextView
        android:id="@+id/about_text_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/blue_aliansce"
        android:gravity="center"
        android:layout_alignParentTop="true"
        android:fontFamily="sans-serif"
        android:textStyle="bold"
        android:textColor="@color/white"
        android:padding="@dimen/menu_title_padding"
        android:text="@string/menu_title"
        android:textSize="@dimen/menu_title" />

    <Button
        android:id="@+id/button_start"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/green_aliansce"
        android:gravity="center_horizontal|center_vertical"
        android:textSize="@dimen/menu_title"
        android:textColor="@color/white"
        android:fontFamily="sans-serif"
        android:text="@string/button_start"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
</RelativeLayout>

CameraOverlayBooks.java
package com.vuforia.samples.Books.ui.ActivityList;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import com.vuforia.samples.Books.R;

public class CameraOverlayBooks extends Activity{

  private Button BackButton;

  public void onCreate(Bundle savedInstanceState){
      super.onCreate(savedInstanceState);
      setContentView(R.layout.camera_overlay_books);

      Button BackButton = (Button) findViewById(R.id.button_back);
      BackButton.setOnClickListener(new View.OnClickListener(){
          public void onClick(View view) {
              Intent trocarTela = new Intent(CameraOverlayBooks.this, AboutScreen.class);
              startActivity(trocarTela);
          }
      });


  }

}

CameraOverlayBooks.xml

<?xml version="1.0" encoding="utf-8"?>

  <RelativeLayout
      android:id="@+id/loading_layout"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:background="@color/semi_transparent_black"
      android:padding="30dip"
      android:visibility="gone" >

      <ProgressBar
          style="@android:style/Widget.ProgressBar"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_centerHorizontal="true"
          android:layout_centerVertical="true" />
  </RelativeLayout>

  <Button
      android:id="@+id/overlay_close_button"
      android:layout_width="50dp"
      android:layout_height="wrap_content"
      android:layout_alignParentRight="true"
      android:layout_alignParentTop="true"
      android:background="@drawable/close_button_background"
      android:visibility="gone" />

  <Button
      android:id="@+id/button_back"
      android:layout_width="50dp"
      android:layout_height="wrap_content"
      android:layout_alignParentLeft="true"
      android:layout_alignParentTop="true"
      android:layout_below="@+id/loading_layout"
      android:layout_toEndOf="@+id/loading_layout"
      android:layout_toRightOf="@+id/loading_layout"
      android:background="@drawable/back_button_background" />

  <TextView
      android:id="@+id/overlay_status"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentBottom="true"
      android:layout_centerHorizontal="true"
      android:layout_marginBottom="70dp"
      android:background="@color/semi_transparent_black"
      android:gravity="center"
      android:paddingBottom="10dp"
      android:paddingLeft="30dp"
      android:paddingRight="30dp"
      android:paddingTop="10dp"
      android:text="@string/status_bar_scanning"
      android:textColor="@color/white"
      android:textSize="@dimen/overlay_status"
      android:visibility="gone" />

  <ImageView
      android:id="@+id/scan_line"
      android:layout_width="match_parent"
      android:layout_height="50px"
      android:src="@drawable/scanline"
      android:scaleType="fitXY"
      android:visibility="gone"/>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<!–
The application’s compatibility with one or more versions of the Android
platform.

      android:minSdkVersion = application's required minimum API level to run
      android:targetSdkVersion = application's targeted API level
  -->
  <uses-sdk
      android:minSdkVersion="14"
      android:targetSdkVersion="22" />

  <uses-feature android:glEsVersion="0x00020000" />

  <!--
       The application requires a camera.

       NOTE: Any application that requests the CAMERA permission but does not
       declare any camera features with the <uses-feature> element will be
       assumed to use all camera features (auto-focus and flash). Thus, the
       application will not be compatible with devices that do not support
       all camera features. Please use <uses-feature> to declare only the
       camera features that your application does need. For instance, if you
       request the CAMERA permission, but you do not need auto-focus or
       flash, then declare only the android.hardware.camera feature. The
       other camera features that you do not request will no longer be
       assumed as required.
  -->
  <uses-feature android:name="android.hardware.camera" />

  <!-- Add this permission to get access to the camera. -->
  <uses-permission android:name="android.permission.CAMERA" />

  <!-- Add this permission to allow opening network sockets. -->
  <uses-permission android:name="android.permission.INTERNET" />

  <!--
      Add this permission to check which network access properties (e.g.
      active type: 3G/WiFi).
  -->
  <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
  <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
  <uses-permission android:name="android.permission.READ_PHONE_STATE" />

  <!--
    NOTE: The setting 'android:launchMode="singleTask"' makes sure
    that the activity can begin only one task and the device can hold only
    one instance of the activity at a time. However, it allows other
    activities to be part of its task (unlike the 'singleInstance' mode).
    It's at the root of the activity stack, but other activities (necessarily
    "standard" and "singleTop" activities) can be launched into the same task.
    If this attribute is not set, the default value 'standard' is used, which
    would allow the activity to be launched multiple times.
  -->
  <application
      android:allowBackup="true"
      android:description="@string/app_description"
      android:icon="@drawable/icon"
      android:label="@string/app_name"
      android:launchMode="singleTask"
      android:theme="@style/SampleAppsTheme">

      <!--
        NOTE: The values in 'android:configChanges' ensure that Android will
        not destroy and re-create the activity when the user flips the
        keyboard, changes the orientation of the device, or the actual or
        physical screen resolution changes, but calls the Activity's
        onConfigurationChanged() function instead.

        NOTE 2: In order to prevent automatic reactions to orientation
        changes in addition to setting proper values for
        'android:configChanges', you also must explicitly specify the screen
        orientation used by the application, either by setting the attribute
        'android:screenOrientation' or in code by calling
        Activity.setRequestedOrientation().
      -->
      <!-- Splash Screen Activity -->

      <activity
          android:name=".ui.ActivityList.ActivitySplashScreen"
          android:configChanges="orientation|keyboardHidden"
          android:noHistory="true"
          android:screenOrientation="portrait">
          <intent-filter>
              <action android:name="android.intent.action.MAIN" />

              <category android:name="android.intent.category.LAUNCHER" />
          </intent-filter>
      </activity>

      <activity
          android:name=".ui.ActivityList.AboutScreen"
          android:configChanges="orientation|keyboardHidden"
          android:screenOrientation="portrait" />

      <activity
          android:name=".ui.ActivityList.CameraOverlayBooks"
          android:configChanges="orientation|keyboardHidden"
          android:screenOrientation="portrait" />

      <activity
          android:name=".app.Books.Books"
          android:configChanges="orientation|keyboardHidden|screenSize|smallestScreenSize"
          android:launchMode="singleTask"
          android:theme="@style/SampleAppsTheme" />


  </application>

jonathan.sky · Maio 25, 2017, 5:05pm

/*Desta maneira tera erro em tempo de compilação, agora rode e vê o que está acontecendo.*/
            
            Button BackButton = (Button) findViewById(R.id.button_back);
            BackButton.setOClickLister(onClick());

             private View.OnClickListener onClick() {
                    return new Button.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                         Intent trocarTela = new Intent(getContext(), AboutScreen.class);
                            startActivity(trocarTela);
                        }
                    };
                }

            private Context getContext(){
            return this;
            }

thiagodbonis · Maio 25, 2017, 5:20pm

Esse codigo que você me enviou está dando problema.
Eu coloquei assim do jeito que me falou, está certo?

Erros:

Error:(26, 39) error: expected
Error:(26, 47) error: expected
Error:(26, 48) error: ‘;’ expected
Error:(26, 49) error: illegal start of type
Error:(26, 50) error: expected
Error:(26, 51) error: ‘;’ expected
Error:(41, 10) error: ‘)’ expected
Error:(46, 2) error: reached end of file while parsing

public class CameraOverlayBooks extends Activity{

    private Button BackButton;

    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.camera_overlay_books);

        BackButton.setOnClickListener(new View.OnClickListener(){
            Button BackButton = (Button) findViewById(R.id.button_back);
            BackButton.setOClickLister(onClick());

            private View.OnClickListener onClick() {
                return new Button.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent trocarTela = new Intent(getContext(), AboutScreen.class);
                        startActivity(trocarTela);
                    }
                };
            }

            private Context getContext(){
                return this;
            }
        }


    }

}

jonathan.sky · Maio 25, 2017, 5:28pm

não copie e cole código, estude antes.

no caso, vou passar a classe.

/extenda de AppCompact ele de compatibilidade além de outras vantagens/

    public class ToastActivity extends AppCompatActivity {

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

            Button BackButton = (Button) findViewById(R.id.button_back);
            BackButton.setOClickLister(onClick());

    }
          private View.OnClickListener onClick() {
                    return new Button.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            Intent trocarTela = new Intent(getContext(), AboutScreen.class);
                            startActivity(trocarTela);
                        }
                    };
                }
       private Context getContext(){
        return this;
    }
      }

thiagodbonis · Maio 25, 2017, 5:32pm

Sim, só que o problema é este “};”, ele da erro:

Error:(24, 45) error: ‘;’ expected
Error:(24, 9) error: illegal start of expression

E retirando o “;” dele, acontece os erros que eu citei a cima, tem algo errado neste seu código.

jonathan.sky · Maio 25, 2017, 6:10pm

O nome da classe estava pouco visível, tinha pego também?

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