6.0权限

import android.Manifest;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.SystemClock;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import java.io.File;
import java.io.IOException;

import static android.content.ContentValues.TAG;

public class MainActivity extends Activity {
    private Button btn3;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn3 = (Button) findViewById(R.id.btn3);
        btn3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                boolean flag = PermissionsUtils.hasPermission(
                        MainActivity.this,
                        Manifest.permission.WRITE_EXTERNAL_STORAGE);
                final String[] PERMISSIONS_STORAGE = {
                        Manifest.permission.READ_EXTERNAL_STORAGE,
                        Manifest.permission.WRITE_EXTERNAL_STORAGE
                };
                if (flag == true) {
                    writeFile();
                } else {
                    if (!shouldShowRequestPermissionRationale(Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
                        showMessageOKCancel("需要读取存储的权限",
                                new DialogInterface.OnClickListener() {
                                    @Override
                                    public void onClick(DialogInterface dialog, int which) {
                                        PermissionsUtils.requestPermission(MainActivity.this, PERMISSIONS_STORAGE);
                                    }
                                }
                        );
                    } else {
                        PermissionsUtils.requestPermission(MainActivity.this, PERMISSIONS_STORAGE);
                    }
                }
            }

            private void showMessageOKCancel(String message, DialogInterface.OnClickListener okListener) {
                new AlertDialog.Builder(MainActivity.this)
                        .setMessage(message)
                        .setPositiveButton("OK", okListener)
                        .setNegativeButton("Cancel", null)
                        .create()
                        .show();
            }
        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case PermissionsUtils.REQUESTCODE:
                if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    // Permission Granted
                    writeFile();
                } else {
                    // Permission Denied
                    Toast.makeText(this, "拒绝授权", Toast.LENGTH_SHORT).show();
                }
                break;
            default:
                super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

    private void writeFile() {
        String fileName = "abc" + SystemClock.currentThreadTimeMillis() + ".txt";
        File file = new File("/storage/emulated/0/" + fileName);
        try {
            file.createNewFile();
            if (file.exists()) {
                Log.i(TAG, "writeFile: " + file.getAbsolutePath());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void readFile() {
        File file = new File("/storage/emulated/0/blank_500_500.png");
        if (file.exists()) {
            Log.i(TAG, "readFile: " + file.getAbsolutePath());
        }
    }
}

import android.app.Activity;
import android.content.pm.PackageManager;
import android.support.v4.app.ActivityCompat;

public class PermissionsUtils {
    final static int REQUESTCODE = 111;
    public static void requestPermission(Activity activity, String[] permisssions) {
        ActivityCompat.requestPermissions(
                activity,
                permisssions,
                REQUESTCODE
        );
    }
    public static boolean hasPermission(Activity activity, String permission) {
        int permissionCode = ActivityCompat.checkSelfPermission(
                activity, permission);
        if (permissionCode != PackageManager.PERMISSION_GRANTED) {
            return false;
        } else {
            return true;
        }
    }
}