无法通过默认相机应用程序的意图拍摄照片

Question

I have three classes. One parent class where button listeners are defined. Second class is for capturing pic and third class gives the path to the pic. However I am facing certain troubles.

Startingactivity.java

 package xxxx.xxxx.xxxx;

import android.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;


public class StartingActivity extends AppCompatActivity {







@Override
protected void onCreate(Bundle savedInstanceState) {
    ActionBar actionBar=getActionBar();
    //actionBar.setTitle();          Put path name here.
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

            new CreateFolder();
   final Captureit captureit=new Captureit();

    Button add,pic,vid,settings;
    add=(Button)findViewById(R.id.addbutton);
    pic=(Button)findViewById(R.id.picbutton);
    vid=(Button)findViewById(R.id.vidbutton);
    settings=(Button)findViewById(R.id.setbutton);


    add.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

        }
    });

        pic.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                captureit.capturepicture();
            }
        });
        vid.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                captureit.capturevideo();
            }
        });

    settings.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

        }
    });

 }
 }

Captureit.java

package sagar.mehar.camera2;

import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.Toast;

import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;



public class Captureit extends AppCompatActivity{

private static final int CAPTURE_VIDEO_ACTIVITY_REQUEST_CODE=200;
private static final int CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE=100;
public static final int MEDIA_TYPE_IMAGE=1;
public static final int MEDIA_TYPE_VIDEO=2;
private Uri fileUri;
public static CreateFolder createFolder=new CreateFolder();
Intent intent;




protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
    if(requestCode==CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE)
    {
        if(resultCode==RESULT_OK)
        {//Image Captured
            Toast.makeText(this, "Image Captured ", Toast.LENGTH_SHORT).show();
        }
        else if(resultCode==RESULT_CANCELED)
        {//User Cancelled Image capture

        }
        else
        {//Image capture failed.
            Toast.makeText(this,"Image Captured Failed",Toast.LENGTH_SHORT).show();
        }
    }
    if(requestCode==CAPTURE_VIDEO_ACTIVITY_REQUEST_CODE)
    {
        if(resultCode==RESULT_OK)
        {
            Toast.makeText(this,"Video Captured",Toast.LENGTH_SHORT).show();
        }
        else if(resultCode==RESULT_CANCELED)
        {

        }else
        {//Video Capture Failed.
            Toast.makeText(this,"Video Captured Failed",Toast.LENGTH_SHORT).show();
        }
    }
}



public void capturepicture() {

    intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);
    intent.putExtra(MediaStore.EXTRA_OUTPUT,fileUri);
    this.startActivityForResult(intent, CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);

}




public void capturevideo()
{
    intent=new Intent(MediaStore.ACTION_VIDEO_CAPTURE);
    fileUri=getOutputMediaFileUri(MEDIA_TYPE_VIDEO);//Create a file to save the video
    intent.putExtra(MediaStore.EXTRA_OUTPUT,fileUri);
    intent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY,1);
    startActivityForResult(intent,CAPTURE_VIDEO_ACTIVITY_REQUEST_CODE);
}
private static Uri getOutputMediaFileUri(int type)
{
    return Uri.fromFile(getOutputMediaFile(type));
}
private static File getOutputMediaFile(int type)
{
    String timeStamp=new SimpleDateFormat("yyyyMMdd__HHmmss").format(new Date());
    File mediaFile;
    if(type==MEDIA_TYPE_IMAGE)
    {
        mediaFile=new File(createFolder.gettPath()+File.separator+"IMG_"+timeStamp+".jpg");
    }
    else if(type==MEDIA_TYPE_VIDEO)
    {
        mediaFile=new File(createFolder.gettPath()+File.separator+"VID_"+timeStamp+".mp4");
    }
    else
    {
        return null;
    }
    return mediaFile;
}

}

Third Class is working properly.

Manifest code is:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="xxxx.xxxx.xxxx"
>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.CAMERA"/>
<uses-feature android:name="android.hardware.camera2"/>
<uses-permission android:name="android.hardware.CAMERA"/>
<uses-permission android:name="android.permission.RECORD_AUDIO"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme" >
    <activity android:name=".StartingActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

</application>

However, whenever I am clicking button to take a pic, app always crashes giving the following log.

01-03 11:01:27.568 11291-11291/xxxx.xxxx.xxxx W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x419b9c98)
01-03 11:01:27.568 11291-11291/xxxx.xxxx.xxxx W/dalvikvm: threadid=1: uncaught exception occurred
01-03 11:01:27.568 11291-11291/xxxx.xxxx.xxxx W/System.err: java.lang.NullPointerException
01-03 11:01:27.569 11291-11291/xxxx.xxxx.xxxx W/System.err:     at android.app.Activity.startActivityForResult(Activity.java:3457)
01-03 11:01:27.569 11291-11291/xxxx.xxxx.xxxx W/System.err:     at android.app.Activity.startActivityForResult(Activity.java:3418)
01-03 11:01:27.570 11291-11291/xxxx.xxxx.xxxx W/System.err:     at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:748)
01-03 11:01:27.570 11291-11291/xxxx.xxxx.xxxx W/System.err:     at xxxx.xxxx.xxxx.Captureit.capturepicture(Captureit.java:72)
01-03 11:01:27.570 11291-11291/xxxx.xxxx.xxxx W/System.err:     at xxxx.xxxx.xxxx.StartingActivity$2.onClick(StartingActivity.java:48)
01-03 11:01:27.570 11291-11291/xxxx.xxxx.xxxx W/System.err:     at android.view.View.performClick(View.java:4463)
01-03 11:01:27.570 11291-11291/xxxx.xxxx.xxxx W/System.err:     at android.view.View$PerformClick.run(View.java:18770)
01-03 11:01:27.571 11291-11291/xxxx.xxxx.xxxx W/System.err:     at android.os.Handler.handleCallback(Handler.java:808)
01-03 11:01:27.571 11291-11291/xxxx.xxxx.xxxx W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:103)
01-03 11:01:27.571 11291-11291/xxxx.xxxx.xxxx W/System.err:     at android.os.Looper.loop(Looper.java:193)
01-03 11:01:27.571 11291-11291/xxxx.xxxx.xxxx W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:5292)
01-03 11:01:27.571 11291-11291/xxxx.xxxx.xxxx W/System.err:     at java.lang.reflect.Method.invokeNative(Native Method)
01-03 11:01:27.571 11291-11291/xxxx.xxxx.xxxx W/System.err:     at java.lang.reflect.Method.invoke(Method.java:515)
01-03 11:01:27.572 11291-11291/xxxx.xxxx.xxxx W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
01-03 11:01:27.572 11291-11291/xxxx.xxxx.xxxx W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
01-03 11:01:27.572 11291-11291/xxxx.xxxx.xxxx W/System.err:     at dalvik.system.NativeStart.main(Native Method)
01-03 11:01:27.572 11291-11291/xxxx.xxxx.xxxx W/dalvikvm: threadid=1: calling UncaughtExceptionHandler
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime: FATAL EXCEPTION: main
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime: Process: xxxx.xxxx.xxxx, PID: 11291
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime: java.lang.NullPointerException
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at android.app.Activity.startActivityForResult(Activity.java:3457)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at android.app.Activity.startActivityForResult(Activity.java:3418)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:748)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at xxxx.xxxx.xxxx.Captureit.capturepicture(Captureit.java:72)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at xxxx.xxxx.xxxx.StartingActivity$2.onClick(StartingActivity.java:48)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at android.view.View.performClick(View.java:4463)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at android.view.View$PerformClick.run(View.java:18770)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at android.os.Handler.handleCallback(Handler.java:808)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:103)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:193)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5292)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:515)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
01-03 11:01:27.574 11291-11291/xxxx.xxxx.xxxx E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)

Please help me, I am stuck at it for hours. Note that, moving the code of Captureit.java to startingactivity.java makes the app works but the code becomes too messy. I just want to make them work in separate classes.

Answer 1

Your second file - captureit.java - cannot be an Activity. An Activity can only be created by calling startActivity() or startActivityForResult() from another activity with an intent. When you call new CaptureIt() the onCreate() method and other activity-specific methods are not called. This means that the activity doesn't have the correct information to do some things - like starting another activity.

Basically you're trying to start the camera activity from an activity that doesn't exist to Android, so it's throwing a NullPointerException.

I'd recommend moving it back into the same file until you understand how moving between activities works in Android.

You could still split the helper methods ( getOutputMediaFile() , etc) into another file to keep the main activity file simple. But don't make it an activity and don't call startActivityForResult from it.