MultiThreadTask.java

package info.papdt.pano.processor;

import android.util.Log;

import static info.papdt.pano.BuildConfig.DEBUG;

public abstract class MultiThreadTask<A, R>
{
	private static final String TAG = MultiThreadTask.class.getSimpleName();
	
	private A mArgument;
	private R[] mResult;
	private int mFinishCount = 0;
	private boolean mFinished = false;
	
	// Should pass in an empty array that have the length of the result
	public MultiThreadTask(A argument, R[] result) {
		mResult = result;
		mArgument = argument;
	}
	
	protected void setResult(int position, R value) {
		synchronized (mResult) {
			mResult[position] = value;
		}
	}
	
	public R[] execute(int threadCount) {
		if (mFinished) return null;
		
		int length = mResult.length;
		
		if (length <= threadCount) {
			threadCount = length;
		}
		
		int taskSize = length / threadCount;
		
		if (DEBUG) {
			Log.d(TAG, "length = " + length + " taskSize = " + taskSize);
		}
		
		for (int i = 0; i < threadCount; i++) {
			final int start = i * taskSize;
			int taskLength = taskSize;
			
			if (i == threadCount - 1) {
				taskLength = length - start;
			}
			
			final int task = taskLength;
			
			if (DEBUG) {
				Log.d(TAG, i + " start = " + start + " length = " + task + " end = " + (start + task));
			}
			
			new Thread(new Runnable() {
				@Override
				public void run() {
					doExecute(mArgument, start, task);
					mFinishCount++;
				}
			}).start();
		}
		
		while (mFinishCount < threadCount); // Wait for finishing
		
		return mResult;
	}
	
	protected abstract void doExecute(A argument, int taskStart, int taskLength);
	
}