パフォーマンスと安定性を強化してアプリの質を高める方法

public void serialize(Context context, String filename, 
                      Serializable object) throws Exception {
  FileOutputStream fOut = 
    context.openFileOutput(filename, Context.MODE_PRIVATE);
  ObjectOutputStream oOut = new ObjectOutputStream(fOut);
  oOut.writeObject(object);
  oOut.close();
}

public Object deserialize(Context context, 
                          String filename) throws Exception {
  FileInputStream fIn = context.openFileInput(filename);
  ObjectInputStream oIn = new ObjectInputStream(fIn);
  Object result = oIn.readObject();
  oIn.close();

  return result;
}

private val executor = Executors.newSingleThreadExecutor()

fun <T : Serializable> serialize(context: Context, filename: String, data: T) {
    executor.execute {
        try {
            context.openFileOutput(filename, Context.MODE_PRIVATE).use { fileOut ->
                ObjectOutputStream(fileOut).use { objOut ->
                    objOut.writeObject(data)
                }
            }
        } catch (e: Exception) {
            e.printStackTrace()
        }
    }
}

fun <T : Serializable> deserialize(context: Context, filename: String, callback: (T?) -> Unit) {
    executor.execute {
        val result: T? = try {
            context.openFileInput(filename).use { fileIn ->
                ObjectInputStream(fileIn).use { objIn ->
                    @Suppress("UNCHECKED_CAST")
                    objIn.readObject() as? T
                }
            }
        } catch (e: Exception) {
            e.printStackTrace()
            null
        }
        callback(result)
    }
}

public class MainActivity extends AppCompatActivity
  implements ComponentCallbacks2 {

  // Other activity code.

  /**
   * Release memory when the UI becomes hidden or when system
   * resources become low.
   * @param level the memory-related event that is raised.
   */
  public void onTrimMemory(int level) {

    if (level >= ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
      // Release memory related to UI elements, such as bitmap caches.
    }
    if (level >= ComponentCallbacks2.TRIM_MEMORY_BACKGROUND) {
      // Release memory related to background processing, such as by
      // closing a database connection.
    }
  }
}

import android.app.Activity
import android.content.ComponentCallbacks2
import android.content.res.Configuration
import android.os.Bundle
import android.util.Log

class MainActivity : Activity(), ComponentCallbacks2 {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        registerComponentCallbacks(this)
    }

    override fun onTrimMemory(level: Int) {
        when {
            level >= ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN -> {
                // Release memory related to UI elements, such as bitmap caches
                Log.d("MemoryTrim", "UI is hidden. Freeing up UI-related resources.")
            }
            level >= ComponentCallbacks2.TRIM_MEMORY_BACKGROUND -> {
                // Release memory related to background processing, such as closing a database connection
                Log.d("MemoryTrim", "App in background. Releasing background resources.")
            }
        }
    }

    override fun onLowMemory() {
        // Handle extreme low-memory situations
        Log.w("MemoryTrim", "System is running low on memory!")
    }

    override fun onConfigurationChanged(newConfig: Configuration) {
        // Required override but not used for memory management
    }

    override fun onDestroy() {
        super.onDestroy()
        unregisterComponentCallbacks(this)
    }
}

public void doSomethingMemoryIntensive() {

  // Before doing something that requires a lot of memory,
  // check whether the device is in a low memory state.
  ActivityManager.MemoryInfo memoryInfo = getAvailableMemory();
    if (!memoryInfo.lowMemory) {
      // Do memory intensive work.
  }
}

// Get a MemoryInfo object for the device's current memory status.
private ActivityManager.MemoryInfo getAvailableMemory() {
  ActivityManager activityManager =
    (ActivityManager) this.getSystemService(ACTIVITY_SERVICE);
  ActivityManager.MemoryInfo memoryInfo = new ActivityManager.MemoryInfo();
  activityManager.getMemoryInfo(memoryInfo);
  return memoryInfo;
}

import android.content.Context

fun Context.isMemoryLow(): Boolean {
    val activityManager = getSystemService(Context.ACTIVITY_SERVICE) as ActivityManager
    val memoryInfo = ActivityManager.MemoryInfo()
    activityManager.getMemoryInfo(memoryInfo)
    return memoryInfo.lowMemory
}

fun doSomethingMemoryIntensive(context: Context) {
    if (!context.isMemoryLow()) {
        // Perform memory-intensive operation
    }
}

// Bad example: Performing time-consuming task on the main thread
public void onClick(View v) {
  // This will block the UI and potentially cause an ANR
  Bitmap bitmap = processBitMap("image.png");
  imageView.setImageBitmap(bitmap);
}

// Good example: Moving time-consuming task to a background thread
public void onClick(View v) {
  new Thread(new Runnable() {
    public void run() {
      // A potentially time-consuming task performed off the main thread
      final Bitmap bitmap = processBitMap("image.png");


      // Use post() to update UI safely from the main thread
      imageView.post(new Runnable() {
        public void run() {
          imageView.setImageBitmap(bitmap);
        }
      });
    }
  }).start();
}

import android.graphics.Bitmap
import android.os.Handler
import android.os.Looper
import android.view.View
import android.widget.ImageView
import java.util.concurrent.Executors

class MyActivity {

    private val executor = Executors.newSingleThreadExecutor()
    private val mainHandler = Handler(Looper.getMainLooper())

    fun onClick(view: View, imageView: ImageView) {
        executor.execute {
            // Perform time-consuming task in background thread
            val bitmap = processBitmap("image.png")

            // Update UI safely on the main thread
            mainHandler.post {
                imageView.setImageBitmap(bitmap)
            }
        }
    }

    private fun processBitmap(filename: String): Bitmap {
        // Simulate bitmap processing (e.g., decoding an image)
        Thread.sleep(2000) // Simulate delay
        return Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888)
    }
}